Volient videogames decrease crime

 

ABSTRACT: Psychological studies predominately find a positive relationship between

violent video game play and aggression. However, these studies cannot account for either

aggressive effects of alternative activities video game playing substitutes for or the possible

selection of relatively violent people into playing violent video games. That is, they lack

external validity. We investigate the relationship between the prevalence of violent video

games and violent crimes. Our results are consistent with two opposing effects. First, they

support the behavioral effects as in the psychological studies. Second, they suggest a larger

voluntary incapacitation effect in which playing either violent or non-violent games decrease

crimes. Overall, violent video games lead to decreases in violent crime.

 

 

1. Introduction

From the sensational crime stories of the 19th century (Comstock and Buckly 1883), to

the garish comic books of the early 20 th century, (Hadju 2009), to today’s violent video

games, Americans have made efforts to reduce children’s access to violent media because of

concerns over their social costs. These concerns may not be unfounded as numerous studies

purport to find that violent media of all sorts, including games, can cause increases in

measured aggression. Aided in part by mounting evidence that violent video game play cause

aggression, states have passed legislation criminalizing the distribution of violent video games

to minors. 1

The research is not clear on how large the increase in aggression caused by these

games. Craig Anderson, a long-time researcher in the effect of violent media on aggression

has contended that “one possible contributing factor [to the Columbine High School killings

was the shooters’ habits of playing] violent video games. [The shooters] enjoyed playing the

bloody shoot-`em-up video game Doom, a game licensed by the U.S. Army to train soldiers to

effectively kill” (quoted in Kutner and Olson 2009). 2

1 In 2010, California passed a law making it a punishable offense for a distributor to sell a banned violent video to a minor. The US Supreme Court struck down this law in June, 2011.

2 In the opening paragraph of his literature review, Anderson (2004) suggested violent video games were

responsible for the recent wave of school shootings since the late 1990s.

3

If violent video games can be shown to cause violence, then laws aimed at reducing

access may benefit society at large. Yet to date, though there is ample evidence that violent

video games cause aggression in a laboratory setting, laboratory stings cannot address issues

of selection or incapacitation. Ward (2010) shows that adolescents who are otherwise

predisposed to violence tend to select into video game play. Dahl and Dellavegna (2009)

suggest that violent movies incapacitate violent crime offenders. Likewise, since the hours it

takes to “beat the game” substitute for some other activity, a complete analysis of video game

effects must consider the opportunity cost of this time. Violence may fall because violent

people are attracted to violent games and because gamers engaged in virtual violence are not

simultaneously engaged in actual violence.

To date, there is no evidence that violent video games cause violence or crime. In fact,

two recently published studies analyzed the effect of violent media (movies and video game

stores) on crime, and found increased exposure may have caused crime rates to decrease

(Dahl and Dellavegna 2009; Ward 2011). These studies, unlike the laboratory studies, were

conducted with observational data, which poses unique scientific challenge to establishing

causality. However, since laboratory studies have never shown that video game violence

causes crime or violence, despite researchers out-of-sample predictions (Anderson 2004),

observational studies may be the only ethical and practical way to test for such a causal effect.

To many in this field, it is logical to assume that if exposure to violent media causes

aggression in the lab, it will therefore cause aggression when exposure occurs non-randomly

outside the laboratory. Psychologists have adapted the general aggression model, or GAM, to

the video game setting (Bushman and Anderson, 2002 and Anderson and Bushman, 2002).

GAM hypothesizes that violent media, including violent video games, increases a person’s

aggressive tendencies through a process of social learning that occurs simultaneous to the

exposure itself. Violent media causes the person to mistakenly develop certain scripts, or rules

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of thumb, that are used to interpret social situations both before they occur, as well as

afterwards. GAM posits, in other words, that violent video games cause aggression by biasing

individuals towards forming incorrect beliefs about relative danger that they are in. Perception

biases towards hostility, therefore, can in turn cause the person to respond in either a “fight or

flight” fashion. It may also permanently alter a person’s point of view, creating an aggressive

personality as an outcome (Bushman and Anderson 2002). A variant of the “rational

addiction” model (Becker and Murphy 1988) may be a fair representation of GAM. The key

insight for GAM is that consumption of a good in one period not only affects current utility

directly but, through a capital stock accumulation mechanism, it also affects future utility

indirectly.

The opportunity cost of playing a video game is not just pecuniary but also includes

lost time. In fact, for many gamers, the value of the time spent playing a game may be worth

much more than the pecuniary cost of the game. This time spent gaming cannot be spent on

other activities, legitimate or otherwise, if time use is rival in consumption. The substitution

patterns from video games may derive more from time use effects than from pecuniary costs

(Becker, 1965). Evidence for video games having a time use component can be found in

Stinebrickner and Stinebrickner (2008). The authors identified a causal effect of studying on

academic performance by utilizing the random assignment of college students to roommates

with a video game console, relative to the counterfactual, which caused students to study less

often, and in turn, to perform worse in school

In this paper, we argue that since laboratory experiments have not examined the time

use effects of video games, which incapacitate violent activity by drawing individual gamers

into extended gameplay, laboratory studies may be poor predictors of the net effects of violent

video games in society. Consequently, they overstate the importance of video game induced

aggression as a social cost. We argue that since both aggression and time use are a

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consequence of playing violent video games, then the policy relevance of violent video game

regulation depends critically on the degree to which the one outweighs the other. If, as we

find in our study, the time use effect of violent video games reduces crime by more than the

aggression effects increase it, then the case for regulatory intervention becomes weaker.

While some early work has been done on the long-term effects of video game play, nearly all

the laboratory evidence that currently exists has only uncovered very short-term effects,

which is when time use effects could be the most important. 3

As with Dahl and Dellavegna (2009) and Ward (2011), we use a proxy for individuals’

exposure to violent video games – the volume of sales of violent video games in a week

among the top 50 best-selling video games from 2005-2008 – and relate it to a marker for

violent behaviors – weekly aggregate violent crime incidents from the National Incident

Based Reporting System (NIBRS). Using time series modeling, as well as an instrumental

variables approach, we estimate the effect of an increased weekly volume of violent video

game sales on the number of criminal incidents recorded to law enforcement over the

subsequent weeks and find that increased violent video games are associated with decreases

in crime rates, similar to Dahl and Dellavegna (2009) and Ward (2011).

One advantage of our approach is that we can attempt to disentangle the separate

effects of both a behavioral change toward more aggression and incapacitation due to time

use. Our results provide some support for the psychological finding that, absent

incapacitation, violent video games lead to more aggression as measured by violent crimes.

However, our results also suggest that this is dominated by possible incapacitation and

selection effects leading to a net reduction in violent crimes. This approach can help guide

3 In Anderson (2004), the author notes the glaring omission of longitudinal studies of effects of violent video

games on aggression in his conclusions on the state of the research, calling for more studies aimed at

investigating the long-term effects. If nothing else, though, this makes our point that the abundance of evidence

that we know does exist only speaks to short-term effects of violent video games on aggression, which is the

purpose of this study here.

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investigators to develop more holistic research designs, such as field experimentation and

other quasi-experimental methodologies, to determine whether the net social costs of violent

games are non-trivial. The main shortcoming of our approach is due to the limitations of our

data on game sales. Unfortunately, the industry does not report cross-sectional variation in

game sales – only the national weekly sales of the top 50 highest grossing games are

available. As a result, our paper follows a methodology similar to Dahl and Dellavegna

(2009), who estimated the impact of violent movies, proxied by daily ticket sales, on crime

using only time series methods.

The paper is structured as follows: the second section our data and methodology. The

third presents and discusses our results. We conclude with a brief discussion of the

implications for public policy.

III. Data and Methodology

Randomized assignment of a treatment with comparison groups used to make

comparative counterfactuals is widely considered the “gold standard” in the social sciences

(Fisher 1935; Campbell and Stanley 1963; Rosenbaum 2002). Yet, it is widely known that

experimentalism may fail to identify true causal effects for a variety of reasons (Berk 2005;

Deaton, 2010; Heckman and Urzua, 2010; Imbens 2010). While others have noted the failure

of researchers in this literature to satisfy the rigorous conditions for establishing causality

(Ferguson and Kilburn 2008; Olson and Kuttner 2009) our study will focus on a separate

statistical challenge not mentioned in these earlier studies: the challenge of internal versus

external validity.

Finding of a positive effect of violent games on aggression does not therefore mean

that violent video games playe will cause crime if the incapacitation effects from time use

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swamp the marginal increase in aggression in the person. By design, laboratory studies – both

by ignoring alternative time use and by treating both treatment and control groups with this

separate effect – cannot be used to guide researchers as to what expect outside the lab. In this

sense, the studies have internal validity, but may not have external validity on the incidence

of socially costly aggression from violent video game play (Campbell and Stanley 1963).

Quasi-experimental methods, such as panel econometric methods, regression discontinuity

and instrumental variables, as well as field experimentation (Harrison and List 2004; Angrist

2006) may be more suitable estimating the social costs of violent video games since they

allow for the estimation of all known and unknown theoretical mechanisms. In this section,

we explain our research design and the data used to overcome some of the limitations of a

purely experimental methodology.

A. Empirical Methodology

The models of video game violence suggest that the effect of violent video game play on

crime will depend on whether a sizable stock of aggressive tendencies accumulates and on the

games’ time use intensities.

Since the theoretical predictions are ambiguous and the policy relevance of the

laboratory studies is unclear, empirical work outside of a laboratory context is warranted.

However, without experimental data, causal inference is problematic. Correlations between

video game play and crime may or may not reflect a causal relationship if the unobserved

determinants of crime are correlated with the determinants of video game play. For instance,

bad weather such as rain or heavy snow which causes individuals to remain at home would

both increase the likelihood of playing video games and decrease the returns to crime through

higher chances of finding a resident at home. Hence, negative correlations between crime and

violent video game play could purely be a consequence of omitted variable bias. Similarly,

video game publishers could strategically release violent video games during periods of time

8

when gamers have a lower value of time. But a low opportunity cost of time would affect both

video game sales and crime. For example, both video game sales and the crime rate increase

during summer when most teenagers are out of school..

One solution to omitted variable bias when there is time-variant heterogeneity is to

employ instrumental variables (IVs). The researcher must have instruments that are strongly

correlated with individual game play but uncorrelated with the determinants of crime. This

approach exploits exogenous variation in video game play that is not due merely to changes in

the determinants of crime providing greater assurance that the estimated effect is causal. We

use the ratings of video games by a video games rating agency as IVs. Our IV strategy

exploits the variation in game sales correlated only with the variation in quality, and thus is

mostly free of variation due to factors related to crime.

Zhu and Zhang (2010) show that consumer reviews of video games are positively

related to game sales. Ratings are valuable pieces of information for video games because

games are complex experience goods for which gamers cannot know their preferences

without playing. Our data on professional ratings contain rich information that communicates

the kinds of information that gamers value in forecasting their beliefs about the game, and as

beliefs and anticipation are drivers of the game sales, we would expect these rating

institutions to play important roles in forming consumer prior beliefs about the game and

therefore their purchases. But we also have some evidence from other industries that would

suggest scores would independently cause purchases to rise, independent of the unobserved

factors that cause expert opinion and purchases to be highly correlated. Reinstein and Snyder

(2005) used exogenous variation in Siskel and Ebert movie ratings due to disruptions in their

pair’s reviewing to determine a causal effect on movie demand. More recently, Hilger Rafert

and Villas-Boas (2010) found that randomly assigned expert scores on bottles of wine in a

retail grocery store caused an increase in sales for the higher rated, but less expensive, wines.

9

While these studies do not confirm that there are exogenous forces in video game ratings that

drive consumer purchases, they are suggestive.

We begin by estimating a standard multivariate regression model of the incidence of

various crimes as functions of, among other controls, the prevalence of non-violent and

violent video games. Our outcome variables of interest, C t , are the total number of reported

criminal incidents in week t as well as the number of such incidents that are classified as

violent. While one might interpret any criminal incident as reflecting some level of

aggression, we interpret violent crimes as reflecting more aggression. While the dataset we

use documents criminal offenses on a daily basis, since the video game sales data are

available only on a weekly basis, we aggregate crimes into weekly measures to focus on

same-week exposure. Accordingly, we employ a simple least squares estimator so as to more

easily instrument for video game exposure. 6

Our main explanatory variables are aggregated current and lagged values of weekly

sales volumes for both non-violent and violent video games. Video games appear to

depreciate quickly with use. This may be because new games are played intensively for a few

weeks after purchase and are not replaced with a new game until after some diminishing

returns have been reached, or it may suggest that firms typically stagger the release dates of

games. We measure the cumulative effect of games with the sales volume of the current

week’s sales, along with the various lags of previous weeks’ sales, so as to capture the effect

of higher volume of gameplay with an unknown time lag to trigger crime.

Our benchmark specification is:

( ) ∑

[ (

)]

[ (

)]

where L  is the lag operator of length  . The number of crime incidents depends on the

exposure to violent video games

and non-violent games . The sum over  of can be

6 Our empirical methodology is in large part based on Dellavegna and Dahl’s (2008) study of the effect of movie

violence on crime.

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interpreted as the cumulative percentage increase over the  weeks in criminal incidents for

each percent increase in violent video games sold in week t while the similar sum for

can

be similarly interpreted for non-violent video games. The trend and month dummies attempt

to account for secular increases and seasonality in video game purchases. The identification of

the parameters is based on the time-series variation in the style of violence in the video

games. Again, we instrument for both types of games using average quality ratings of the

games on the market that week.

The measured effect from this specification can represent a confluence of multiple

effects. It is possible for there to be a positive behavioral effect, as found in the laboratory,

and a negative voluntary incapacitation effect. This specification will typically only measure

the net effect. However, it may be possible to disentangle the behavioral effects from the

incapacitation effect from the estimated cumulative effects from non-violent and violent

games. Both should incorporate incapacitation effects but only the former will include a

behavioral effect toward aggression. The difference between the two provides an estimate of a

pure aggression effect.

Besides the benchmark specification we employ two additional specifications as

robustness checks. These specifications identify specific segments of the population and

locations where we expect a differential a gaming-to-violence link, e.g. crimes committed by

teens and young adults and those committed at high school and college campuses. For each

crime incident, NIRBS provides information on the age of the offender and on the location of

the incident. In the first robustness check, we select a sun-sample of offenders aged between

15 and 30 years and compare these results to the results obtained from a sub-sample of

offenders who are 35 to 50 years old. In our second check, we extend our estimation

procedure to compare the effects on the number of incidents reported on school campuses to

the number committed at other locations.

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B. Video Game Sales Data

Our treatment variables for video game play are derived from the volume of video

game unit sales data from VGChartz 7 . Beginning consistently in 2005, this site has provided

unit sales volume information for each of the top 50 selling video console based games each

week. Among other information, volumes are reported worldwide as well as for several

geographical areas including USA, Japan, Europe, Middle East, Africa or Asia. In our sample

period 2005 to 2008 the VGChartz dataset contains 1,091 different titles over the 208 weeks

for the US with some of these titles being the same game for different gaming consoles. In

sum, the games are provided from 47 different publishers and designed for nine different

gaming consoles. While VGChartz includes the top 50 selling games each week, it only

covers a portion of all sales in the US video game market. A game’s week of release is almost

always its top selling week. Figure 1 indicates that most games stay in the top 50 for only a

few weeks. Moreover, as Figure 2 indicates, the top selling games sell much more than even

the lower ranked top 50 games. These features suggest that there is considerable week-to-

week variation in the games, and the types of games, being played. According to the

Entertainment Software Association (ESA) 8 VGChartz account for about one-quarter of all

units in 2005 (ESA Annual Report, 2010). The ESA also includes sales of non-console based

games such as computer and smartphone games. Still, this fraction rises to almost one-half in

2008.

Our measure of violent videogame content stems from the Entertainment Software

Rating Board (ESRB). 9 This non-profit body independently assigns a technical rating (E, E10,

T, M, and A) which defines the audience the game is appropriate for where E classifies games

for everybody, E10 for everyone aged 10 and up, T for teens, M games for a mature audience,

and A for adult content. In addition, ESRB provides detailed description of the content in each

7 http://www.vgchartz.com/

8 http://www.theesa.com – The reported numbers from ESA also include games for personal computers which

amount to about 10 percent of the market each year and are intentionally not included in VGChartz.

9 http://www.esrb.org

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game on which the rating was made, including the style of violence, e. g. language, violence,

or adult themes. For all of the 1,091 titles in our sample we collected the appropriate ESRB-

rating and all content descriptors. Based on this content information we identify 762 non-

violent and 329 violent games, of which 105 titles are described as intensely violent. Almost

all violent games are rated T or M. All intensely violent games are rated M. Since most of the

policy concern stems from these intensely violent games, these are the games we concentrate

on. 10 Merging both data sources together we can construct measures of the aggregate unit

sales of non-violent and intensely violent video games for each week. The weekly sales are

pictured in Figure 3 for all games and for intensely violent games. Overall, the two graphs

follow a similar pattern with a peak around the Christmas gift purchasing period. In the mid of

2008, however, the intense violent games seem to account for almost all sales of the violent

games.

As argued above the prevalence of video games in a week is not randomly distributed

over the sample and therefore may be endogenous. For instance, if changing economic

conditions that caused a rise in unemployment, and in turn crime rates, may also have caused

leisure activities like video games to rise, then we might observe positive correlations

between video game play and crime that is driven purely by these changing economic factors

(Raphael and Winter-Ebmer 2001; Gould, Weinberg and Mustard 2002). We address the

potential endogeneity of video games with instrumental variables using expert review of each

title as an instrument for purchases.

Our expert review data comes from the GameSpot website. 11 GameSpot provides

news, reviews, previews, downloads and other information for video games. Launched in

May 1996 GameSpot’s main page has links to the latest news, reviews, previews and portals

10 We have also performed our analysis for the broader “violent” and “intensely violent” definition of a violent

game. Qualitatively, all of our general results described below hold however parameter estimates are smaller (in

absolute value terms) and are less precisely estimated.

11 http://www.gamespot.com

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for all current platforms. It also includes a list of the most popular games on the site and a

search engine for users to track down games of interest. The GameSpot staff reviewed all but

a handful of the games in our sample and rated the quality of the titles on a scale from 1 to 10

with 10 being the best possible rank. These so-called GameSpot-scores assigned to each game

are intended to provide an at-a-glance sense of the overall quality of the game. The overall

rating is based on evaluations of graphics, sound, gameplay, replay value and reviewer’s tilt.

A possible issue with this measure is that GameSpot changed the rating system in mid of 2007

to employ guidelines and a philosophy focusing more on a prospective customer rather than a

hardcore-fan that the reviewers had focused on before. Nevertheless, the five mentioned

aspects are essential parts of a game that are still reviewed in detail by a GameSpot reviewer

but will not get an aspect-specific rating score anymore. We do not consider this change in the

GameSpot focus to noticeably affect the overall GameSpot-score.

We expect the quality rating of the games to be positively correlated with their sales as

better-rated games usually are more highly demanded. It is possible that some games have the

opposite relationship if they are based on a popular tie-in from a movie, e. g. Harry Potter, or

sequels, e. g. the Final Fantasy series. Developers know that these games will sell well due to

their popular tie-in which may lower the returns to investment in game quality. However, in

table 2 we show that, a game title’s weekly sales are positively related to the Game Spot score

for games of different violence profiles.

C. Crime Data

For our measure of weekly crime, we used the National Incident Based Reporting

System (NIBRS). NIBRS is a federal data collection program begun by the Bureau of Justice

Statistics in 1991 for gathering and distributing detailed information on criminal incidents for

participating jurisdictions and agencies. Participating agencies and states submit detailed

information about criminal incidents not contained in other data sets, such as the Uniform

Crime Reports. For instance, whereas the Uniform Crime Reports contain information on all

14

arrests and cleared offenses for the eight Index crimes, NIBRS consists of individual incident

records for all eight index crimes and the 38 other offenses (Part II offenses) at the calendar

date and hourly level (Rantala and Edwards 2001). A potential drawback of NIBRS is that

many law enforcement agencies do not participate. [Need a sentence or two here Scott] We

aggregate across only the jurisdictions that participated during each of our sample years.

Because of the detailed information about the incident, including the precise time and date of

the incident, economists such as Dahl and Dellavegna (2009), Card and Dahl (2009), Jacob

and Moretti (2003) and Lefgren, Jacobs and Moretti (2007) have used it for event studies. In

our case, we exploit detailed information about the age of offenders and the crime’s location –

on school campuses or not – for our robustness checks.

Crimes follow a seasonal pattern. Figure 4 indicates a consistent pattern of gradual

increases in both violent and non-violent crimes from winter to summer. Our method was

developed to account for seasonality in both of our main variables of interest crime and

games. Much of the seasonality in crimes is believed to be due to weather while seasonality in

games is likely due to holiday gift giving (Lefgren, Jacobs and Moretti 2007). Failure to

address this will likely lead to spurious correlations. As indicated above, we accommodate

this in two ways. First, month dummy variables should capture much of the seasonality.

Second, using Game Spot scores as IVs should isolate the variation in game sales due to game

quality.

Our final sample includes 208 weekly observations on video games sales and crimes

from early 2005 through 2008. However, eight observations are excluded from final

regressions because of the use of lagged video game sales. Table 3 reports basic descriptive

statistics for our sample.

IV. Results

A. Basic Results

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Our basic regression results are presented in Tables 4 and 5. Table 4 reports estimates

of specifications for various lags of the effect video games sales on all crimes. Video games

are separated between those that the ESRB rated as “intensely violent” and those that are not.

Recall that the lesser rating of merely “violent” does not warrant an ESRB rating of “M.” 12

Control variables include month dummies to capture seasonality and a time trend to capture

any secular trend. The columns from left to right add more lags of video games to the

specification so as to measure possible inter-temporal effects of game purchases in one week

affecting crime in subsequent weeks through continued play. Finally, each regression employs

a 2SLS estimator with the same set of current and eight lags of Game Spot scores averaged

over intensely violent games and over games that are not intensely violent. Since the

specifications are over-identified, we test for possible endogeneity of the instrument set. As

expected, in all cases, we fail to reject the exogeneity of Game Spot scores with respect to the

level of crime. 13

The estimated effect of video games sales in any single week is small. Most individual

coefficient estimates are negative but few are significantly different from zero. It appears that

lags of up to five weeks of video game sales may be associated with current crime. It is not

clear from this table whether violent games have a different effect from those that are not

violent. For ease of comparison, we report the sum of the coefficients for various lags for both

in the top panel of Table 6 to calculate the cumulative effect of a change in video games over

time. Here it becomes clearer that video games are estimated to have an overall negative

effect on crime for specifications that include from two to six lags. That is, both violent and

non-violent games are associated with reductions in crimes. However, the effect is small.

Since our specification is double log, these estimates can be interpreted as elasticities with

12 Unreported regressions comparing games that are either “intensely violent” or “violent” versus all other games

generally yield much less precisely estimated parameters.

13 Estimates assuming that game sales are exogenously determined typically generated smaller (in absolute value

terms) and much less precisely estimated coefficients.

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values of up to -0.025 for non-violent games and -0.010 for violent games. These estimates

suggest that, over all the mechanisms through which videogame play can affect crime, the net

effect is to reduce crime.

As mentioned above, these estimates may also allow us to make some inferences that

distinguish between potential mechanisms. While both violent and non-violent games are

hypothesized to have incapacitation effects, only violent games are hypothesized to alter

behaviors. Indeed, the top panel of Table 6 indicates that the difference in effects between

violent and non-violent games is for violent games to reduce crime by a smaller amount and

that this difference is statistically significant for specifications that include between one and

five lags. Moreover, it is possible that the incapacitation effect for violent games is greater

than for non-violent games, though we cannot test this hypothesis. If so, the difference of

these estimates may represent a downwardly biased estimate of a behavioral effect. This

provides some support for the laboratory findings of a reinforcing behavioral effect that

partially counterbalances the incapacitation effect.

Table 5 repeats these specifications where the dependent variable is now the log of

violent crimes. By doing so, we focus on criminal acts that clearly entail an element of

aggression. Again, we include various lags for the effects of video games and, again, more

individual estimates are negative than positive but few are significantly different from zero.

The bottom panel of Table 6 reports the aggregation of the lagged video game coefficients to

calculate the cumulative effects. From this panel we usually find an overall negative effect of

video games on the number of violent criminal incidents. These estimates are quite similar to

those for all crimes in upper panel of this table. If anything, these parameter estimates are

slightly larger (in absolute value terms) and aggregations with more specifications yield

results significantly different from zero. These estimates indicate that both violent and non-

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violent video game play is generally associated with reductions in the number of violent

crimes.

The test for a difference in the effects for violent and non-violent games may be more

informative. There are no known previously hypothesized mechanisms through which non-

violent games would affect violent crimes. We propose that the appropriate test for violent

video games affecting violent behavior is the difference in these effects by game type. In this

case, the marginal effect of violent video games, relative to non-violent games, is to increase

violent crimes. Decomposing the two effects suggests that a one hundred percent increase in

violent video game sales implies an incapacitation effect reducing violent crime by as much

as 2.6% and an aggression effect increasing violent crimes by as much as 1.5%.

B. Age of Offender Results

A potential robustness check is to examine the effects of video games on criminal

offenders by age of offender. While the age profile of video game players is increasing, video

games are still primarily played by children, teens and younger adults. For most offenses, the

NIBRS data records information on the age of the offenders for an incident. We separately

examine the effects of video game sales on offenders aged 15-30, the prime video game

playing population, versus those 35-50, a population for which video game play is not as

popular. If our basic results were spurious and did not reflect any direct link between video

game play and criminal acts, we would have no reason to expect a differential effect by age

group. In contrast, under our hypotheses, we would expect larger effects for the younger

group.

Table 7 reports cumulative estimates for both these younger and older groups. The

specifications are otherwise identical to those reported in Table 4. However, rather than report

the individual estimates as in Tables 4 and 5, we report the estimated sums over all lags as in

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Table 6. As before, specifications with lags from between two and five achieve some level of

statistical significance for both the young and the old. The estimated effects of both violent

and non-violent video games are both negative, as before. And, as before, violent video games

decrease crime by less than do non-violent video games. That is, there are few, if any,

qualitative differences across the two groups.

Table 8 reports cumulative estimates where the dependent variable is violent crimes,

for both these younger and older groups. The specifications are otherwise identical to those

reported in Table 5 and again we report the estimated sum of effects over all lags as in Table

6. Now, there are noticeable differences across the two groups. None of the estimates for the

older group approach traditional levels of statistical significance. In contrast, the estimates for

the younger group are generally larger (in absolute value) and many are statistically

significant. In addition, the differences in estimates between violent and nonviolent games are

often statistically significant. We again find that, for the younger group, non-violent games, as

well as violent games, reduce the number of violent crimes. In these specifications, the

measured by the difference between the coefficients in the two rows which is about 0.06.

Thus, this is evidence that the behavioral effect of violent video games on violent behavior is

found only within the younger population that tends to play video games more intensively.

C. On Campus Results

Another potential robustness check is to distinguish between crimes committed at

schools and colleges and those committed elsewhere. Schools and colleges tend to aggregate

people who are of video game playing age. The NIBRS data record the location of each

incident as a categorical variable where one possible choice out of eleven is “school or college

campus.” One advantage of this variable over the age of offender variable is that it is recorded

for all incidents while the age of offender can be missing if no one witnessed the incident in

progress. One disadvantage is that crimes committed at schools and colleges need not be

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committed by a member of the younger video game playing demographic, though most are.

Perhaps a bigger problem is that many of the younger video game playing population commit

crimes away from schools. Finally, since such a small number of crimes are committed on

campus, we may lose statistical power for that sub-sample while the off-campus sub-sample

will be quite similar to the overall sample.

Table 9 reports cumulative estimates for both crimes committed on campuses and

those committed off-campus. The specifications are otherwise identical to those reported in

Table 4 but we report the estimated cumulative effect over all lags as in Table 6. As before,

specifications with lags from between two and five achieve some level of statistical

significance for both the young and the old. The pattern of estimated effects for both violent

and non-violent video games is similar to before except that they are much larger for the on-

campus sample than off-campus sample. In the lower panel, the estimates are qualitatively

similar to the base results in Table 6. However, the upper panel estimates are about five times

larger. Other than the difference in magnitudes, the pattern of effects on-campus is

unchanged. There is still a negative effect for non-violent video games in columns 2-5 that we

interpret as an incapacitation effect. The estimated effect for violent video games is

statistically significantly smaller (in absolute value) and we interpret the difference as a

possible estimate of a behavioral effect of violent video games on crime for this sub-sample.

Table 10 reports cumulative estimates where the dependent variable is the number of

violent crimes, for both crimes on and off campus. The specifications are otherwise identical

to those reported in Table 2 and again we report the estimated sum of effects over all lags as

in Table 6. In this case, fewer effects are estimated to be significantly different from zero.

However, the pattern is similar to those for all crimes in table 9. The magnitudes are about

five times larger for the on-campus sub-sample relative to the off-campus sub-sample. As

20

expected, the off-campus results are more similar our basic results reported in the bottom

panel of Table 6.

V. Conclusion

Content regulation of the video game industry is usually predicated on the notion that

the industry has large and negative social costs through games’ effect on aggression. Many

researchers have argued that these games may also have caused extreme violence, such as

school shootings, because laboratory evidence has found an abundance of evidence linking

gameplay to aggression. Yet few studies before this one had examined the impact of these

games on crime, with the exception of Ward (2011) and Dahl and Dellavegna (2009).

Consistent with these studies, we find that the social costs of violent video games may be

considerably lower, or even non-existent, once one incorporates the time use effect into

analysis.

These analyses are suggestive of the hypothesis that violent video games, like all video

games, paradoxically may reduce violence while increasing the aggressiveness of individuals

by simply shifting these individuals out of alternative activities where crime is more likely to

occur. Insofar as our findings suggest that the operating mechanism by which violent

gameplay causes crime to fall is the gameplay itself, and not the violence, then regulations

should be carefully designed so as to avoid inadvertently reducing the time intensity, or the

appeal, of video games.

Our findings also suggest unique challenges to game regulations. Because GAM

proposes that the individual playing violent video games is developing, accidentally, a biased

hermeneutic towards people wherein they believe they are in danger, then the decrease in

violent outcomes that we observe in our study – the incapacitation effect from time use – may

21

be masking the long-run harm to society if these violent behaviors are developing within

gamers. This suggests that regulation aimed at reducing violent imagery and content in games

could in the long-run reduce the aggression capital stock among gamers, but potentially also

cause crime to increase in the short-run if the marginal player is being drawn out of violent

activities. This may be too costly a tradeoff, and may not pass any cost-benefit test. But

another possibility is that individuals who play games could be regularly taught to recognize

these errors in their framing of situations, which theoretically would reduce the aggressive

capital and thus reduce any negative outcome that is determined by the amount of aggression

the person has built up, without losing the short-run gains from crime reduction.

22

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24

Figure 1

25

Figure 2

26

Figure 3

27

Figure 4

28

Table 1

Unit Sales of Video Games (millions) from VGChartz and ESA

Year VGChartz ESA Pct

2005 56.7 240.7 23.6%

2006 76.2 267.8 28.5%

2007 107.0 298.2 35.9%

2008 141.3 273.5 51.7%

VGChartz from authors’ calculations and ESA from

http://www.theesa.com/facts/pdfs/VideoGames21stCentury_2010.pdf.

29

Table 2

The Effect of Game Quality (Game Spot Score) on Log Sales

All Intensely Violent Not Intensely Violent

Games Games Games

GameSpot

Score

0.0803** 0.1221** 0.0769**

(0.0060) (0.0181) (0.0065)

Week of

Release

-0.0039** -0.0081** -0.0036**

(0.0002) (0.0008) (0.0003)

Trend 0.0058** 0.0040** 0.0060**

(0.0001) (0.0003) (0.0001)

February -0.0902* -0.2169* -0.0663+

(0.0361) (0.1020) (0.0385)

March -0.0212 -0.0576 -0.0081

(0.0348) (0.0967) (0.0371)

April -0.1770** -0.3466** -0.1361**

(0.0344) (0.0945) (0.0369)

May -0.2838** -0.4069** -0.2485**

(0.0355) (0.1004) (0.0378)

June -0.1663** -0.3593** -0.1217**

(0.0363) (0.1036) (0.0386)

July -0.2251** -0.5266** -0.1732**

(0.0358) (0.1059) (0.0378)

August -0.3607** -0.6881** -0.3126**

(0.0364) (0.1151) (0.0381)

September -0.2700** -0.4117** -0.2422**

(0.0358) (0.1200) (0.0374)

October -0.1326** 0.0065 -0.1333**

(0.0365) (0.1159) (0.0383)

November 0.6122** 0.6812** 0.6051**

(0.0361) (0.1052) (0.0382)

December 1.2038** 1.1363** 1.2153**

(0.0349) (0.1073) (0.0367)

Constant -4.8503** -0.5994 -5.3472**

(0.2957) (0.8309) (0.3189)

Observations 10,648 1,345 9,303

R-squared 0.38 0.40 0.38

Standard errors in parentheses

+ significant at 10%; * significant at 5%; ** significant at 1%

30

Table 3

Summary Statistics

Variable Mean Std. Dev.

Ln All Video Game Sales 0.407 0.632

Ln Intensely Violent Video Game Sales -1.900 1.037

Ln Not Intensely Violent Video Game Sales 0.781 0.340

Average GameSpot Score 7.634 0.435

Average Intensely Violent GameSpot Score 8.546 0.646

Average Not Intensely Violent GameSpot Score 7.506 0.468

Ln All Crimes 10.889 0.085

Ln Violent Crimes 9.967 0.083

Ln All Crimes on Campuses 7.463 0.421

Ln Violent Crimes on Campuses 6.663 0.506

Ln All Crimes Not on Campuses 10.852 0.091

Ln Violent Crimes Not on Campuses 9.925 0.091

Ln All Crimes Offender Aged 15-30 9.854 0.068

Ln Violent All Crimes Offender Aged 15-30 9.360 0.084

Ln All Crimes Offender Aged 35-50 9.040 0.082

Ln Violent All Crimes Offender Aged 35-50 8.603 0.095

Descriptive statistics of the 200 observations used in later tables.

31

Table 4

The Effects of Video Game Sales on the Log of both Violent and Non-Violent Crime

(1) (2) (3) (4) (5) (6) (7)

Ln Video Game Sales

Not Intensely Violent

-0.028 0.029 0.030 0.041 0.042 0.032 0.044

(0.60) (0.50) (0.44) (0.54) (0.52) (0.40) (0.55)

Ln VG Sales Not

Intensely Violent lag 1

-0.130+ -0.110 -0.090 -0.089 -0.099 -0.088

(1.92) (1.35) (1.03) (1.03) (1.15) (1.02)

Ln VG Sales Not

Intensely Violent lag 2

-0.131+ -0.098 -0.095 -0.044 -0.040

(1.71) (1.16) (1.13) (0.50) (0.46)

Ln VG Sales Not

Intensely Violent lag 3

-0.068 -0.067 -0.064 -0.075

(0.91) (0.88) (0.86) (0.90)

Ln VG Sales Not

Intensely Violent lag 4

0.010 0.042 0.029

(0.12) (0.53) (0.35)

Ln VG Sales Not

Intensely Violent lag 5

-0.125+ -0.126+

(1.73) (1.72)

Ln VG Sales Not

Intensely Violent lag 6

0.026

(0.30)

Ln Intensely Violent

Video Game Sales

-0.009 0.014 0.019 0.030 0.031 0.023 0.026

(0.44) (0.56) (0.64) (0.94) (0.94) (0.71) (0.81)

Ln Intensely Violent

VG Sales lag 1

-0.055+ -0.043 -0.029 -0.029 -0.034 -0.027

(1.77) (1.11) (0.70) (0.69) (0.83) (0.65)

Ln Intensely Violent

VG Sales lag 2

-0.063+ -0.044 -0.042 -0.021 -0.017

(1.72) (1.06) (1.02) (0.49) (0.39)

Ln Intensely Violent

VG Sales lag 3

-0.048 -0.047 -0.047 -0.051

(1.41) (1.27) (1.29) (1.22)

Ln Intensely Violent

VG Sales lag 4

0.001 0.011 0.006

(0.04) (0.29) (0.15)

Ln Intensely Violent

VG Sales lag 5

-0.036 -0.032

(1.10) (0.91)

Ln Intensely Violent

VG Sales lag 6

-0.000

(0.01)

Sample includes 200 weekly observations from 2004-2008. Month dummy variables and a time trend were also

included but are not reported. Average GameSpot scores for intensely violent and not and for the current period

and eight lags are used as IVs. The Sargon statistic for over-identification always fails to reject the exogeneity of

the instrument set. Absolute value of z-statistics in parentheses. + significant at 10%; * significant at 5%; **

significant at 1%.

32

Table 5

The Effects of Video Game Sales on the Log of Violent Crime

(1) (2) (3) (4) (5) (6) (7)

Ln Video Game Sales

Not Intensely Violent

-0.061 0.006 0.012 -0.001 0.001 -0.015 -0.006

(1.21) (0.09) (0.16) (0.02) (0.01) (0.17) (0.07)

Ln VG Sales Not

Intensely Violent lag 1

-0.154* -0.138 -0.109 -0.107 -0.114 -0.108

(2.04) (1.49) (1.14) (1.12) (1.22) (1.16)

Ln VG Sales Not

Intensely Violent lag 2

-0.147+ -0.138 -0.134 -0.099 -0.093

(1.70) (1.50) (1.46) (1.04) (0.98)

Ln VG Sales Not

Intensely Violent lag 3

0.001 0.003 0.009 -0.009

(0.01) (0.04) (0.11) (0.10)

Ln VG Sales Not

Intensely Violent lag 4

0.009 0.031 0.029

(0.11) (0.35) (0.31)

Ln VG Sales Not

Intensely Violent lag 5

-0.072 -0.078

(0.93) (0.99)

Ln VG Sales Not

Intensely Violent lag 6

0.041

(0.44)

Ln Intensely Violent

Video Game Sales

-0.024 0.001 0.003 0.007 0.009 0.000 0.003

(1.15) (0.04) (0.10) (0.20) (0.24) (0.01) (0.08)

Ln Intensely Violent

VG Sales lag 1

-0.060+ -0.050 -0.031 -0.030 -0.036 -0.033

(1.73) (1.14) (0.68) (0.66) (0.80) (0.72)

Ln Intensely Violent

VG Sales lag 2

-0.066 -0.062 -0.060 -0.044 -0.040

(1.61) (1.37) (1.32) (0.97) (0.87)

Ln Intensely Violent

VG Sales lag 3

-0.020 -0.017 -0.016 -0.025

(0.54) (0.42) (0.41) (0.54)

Ln Intensely Violent

VG Sales lag 4

-0.001 0.000 0.000

(0.02) (0.00) (0.00)

Ln Intensely Violent

VG Sales lag 5

0.011 -0.012

(0.30) (0.30)

Ln Intensely Violent

VG Sales lag 6

0.011

(0.24)

Sample includes 200 weekly observations from 2004-2008. Month dummy variables and a time trend were also

included but are not reported. Average GameSpot scores for intensely violent and not and for the current period

and eight lags are used as IVs. The Sargon statistic for over-identification always fails to reject the exogeneity of

the instrument set. Absolute value of z-statistics in parentheses. + significant at 10%; * significant at 5%; **

significant at 1%.

33

Table 6

The Cumulative Effect of Video Games on Crimes

Aggregate Effect on All Crimes (from Table 4)

Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Coefs.

-0.028 -0.102 -0.213* -0.216* -0.203+ -0.257* -0.230+

(0.046) (0.062) (0.096) (0.105) (0.122) (0.124) (0.139)

Intensely

Violent Coefs.

-0.009 -0.041 -0.088* -0.093* -0.088+ -0.104* -0.096+

(0.020) (0.027) (0.041) (0.044) (0.050) (0.050) (0.056)

Chi-Sq test of

difference

0.42 2.70+ 4.75* 3.83* 2.40 4.07* 2.50

Aggregate Effect on Violent Crimes (from Table 5)

Violent/

All Crimes

Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Coefs.

-0.061 -0.148* -0.272* -0.247* -0.227+ -0.260* -0.224

(0.050) (0.069) (0.109) (0.116) (0.134) (0.135) (0.148)

Intensely

Violent Coefs.

-0.024 -0.061* -0.113* -0.107* -0.099+ -0.108* -0.095

(0.021) (0.030) (0.046) (0.048) (0.054) (0.055) (0.056)

Chi-Sq test of

difference

1.36 4.44* 5.99* 4.10* 2.45 3.40* 1.95

For both the top and bottom panels, each column represents results from a separate instrumental variables

regression. Each row reports the sum of coefficients for a variable for different possible lag lengths. Not

reported are coefficients of month dummies and a time trend. Absolute value of z-statistics in parentheses. +

significant at 10%; * significant at 5%; ** significant at 1%

34

Table 7

The Effect of Video Games on All Crimes by Offender Age

Aged 15-30 Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.028 -0.098 -0.182* -0.178+ -0.167 -0.218+ -0.214

(0.046) (0.061) (0.092) (0.100) (0.115) (0.117) (0.134)

Intensely

Violent Games

-0.012 -0.043 -0.079* -0.081+ -0.077+ -0.093* -0.093+

(0.019) (0.026) (0.039) (0.042) (0.046) (0.047) (0.054)

Chi-Sq test of

difference

0.32 2.31 3.56+ 2.62 1.66 3.04+ 2.18

Aged 35-50 Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.020 -0.089 -0.236* -0.210+ -0.214 -0.243+ -0.235

(0.049) (0.068) (0.112) (0.117) (0.136) (0.138) (0.157)

Intensely

Violent Games

-0.014 -0.042 -0.103* -0.096* -0.098+ -0.105+ -0.102

(0.021) (0.029) (0.047) (0.049) (0.055) (0.056) (0.062)

Chi-Sq test of

difference

0.05 1.37 4.01* 2.63 1.99 2.69 1.91

For both the top and bottom panels, each column represents results from a separate instrumental variables

regression. Each row reports the sum of coefficients for a variable for different possible lag lengths. Not reported

are coefficients of month dummies and a time trend. Absolute value of z-statistics in parentheses. + significant at

10%; * significant at 5%; ** significant at 1%

35

Table 8

The Effect of Video Games on Violent Crimes by Offenders Age

Aged 15-30 Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.034+ -0.057* -0.090* -0.087* -0.100* -0.087+ -0.059

(0.019) (0.025) (0.038) (0.040) (0.048) (0.051) (0.057)

Intensely

Violent Games

-0.010 -0.018+ -0.031+ -0.029+ -0.034+ -0.028 -0.017

(0.008) (0.011) (0.016) (0.017) (0.019) (0.021) (0.022)

Chi-Sq test of

difference

4.32* 6.48** 6.84** 5.61* 5.11* 3.54+ 1.40

Aged 35-50 Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.023 -0.021 -0.028 -0.011 0.005 0.020 0.046

(0.016) (0.020) (0.028) (0.033) (0.040) (0.043) (0.048)

Intensely

Violent Games

-0.008 -0.006 -0.009 -0.002 0.003 0.009 0.019

(0.007) (0.009) (0.012) (0.014) (0.016) (0.017) (0.019)

Chi-Sq test of

difference

1.94 1.42 1.24 0.20 0.00 0.17 0.84

For both the top and bottom panels, each column represents results from a separate instrumental variables

regression. Each row reports the sum of coefficients for a variable for different possible lag lengths. Not reported

are coefficients of month dummies and a time trend. Absolute value of z-statistics in parentheses. + significant at

10%; * significant at 5%; ** significant at 1%

36

Table 9

The Aggregate Effect of Video Games on All Crimes by Campus Location

Crimes on

Campus

Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.041 -0.434 -0.837* -1.126* -1.099+ -1.381* -0.976

(0.266) (0.308) (0.417) (0.486) (0.567) (0.600) (0.724)

Intensely

Violent Games

0.018 -0.174 -0.340* -0.465* -0.458* -0.557* -0.399

(0.112) (0.133) (0.176) (0.203) (0.231) (0.242) (0.289)

Chi-Sq test of

difference

0.13 1.97 4.00* 5.14* 3.40+ 5.05* 1.70

Crimes off

Campus

Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.024 -0.088+ -0.192* -0.187+ -0.175 -0.222+ -0.208

(0.045) (0.061) (0.095) (0.103) (0.120) (0.121) (0.137)

Intensely

Violent Games

-0.008 -0.035 -0.080* -0.081+ -0.076 -0.091+ -0.087

(0.019) (0.026) (0.040) (0.043) (0.049) (0.049) (0.055)

Chi-Sq test of

difference

0.30 2.04 3.95* 2.93+ 1.80 3.15+ 2.09

For both the top and bottom panels, each column represents results from a separate instrumental variables

regression. Each row reports the sum of coefficients for a variable for different possible lag lengths. Not

reported are coefficients of month dummies and a time trend. Absolute value of z-statistics in parentheses. +

significant at 10%; * significant at 5%; ** significant at 1%

37

Table 10

The Effect of Video Games on Violent Crimes by Campus Location

Crimes on

Campus Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

0.048 -0.376 -0.758 -1.052+ -0.953 -1.265+ -0.810

(0.302) (0.353) (0.456) (0.550) (0.649) (0.688) (0.832)

Intensely

Violent Games

0.039 -0.171 -0.327 -0.455+ -0.422 -0.529+ -0.349

(0.128) (0.152) (0.201) (0.230) (0.263) (0.278) (0.332)

Chi-Sq test of

difference

0.00 0.93 2.31 3.27+ 1.81 3.06+ 0.82

Crimes off

Campus Number of Lags Included

0 1 2 3 4 5 6

Not Intensely

Violent Games

-0.061 -0.136* -0.255* -0.219+ -0.200 -0.224 -0.202

(0.050) (0.069) (0.109) (0.116) (0.134) (0.137) (0.153)

Intensely

Violent Games

-0.025 -0.056+ -0.106* -0.095+ -0.088 -0.093+ -0.086

(0.021) (0.030) (0.046) (0.048) (0.055) (0.055) (0.061)

Chi-Sq test of

difference

1.32 3.74+ 5.02* 3.14+ 1.86 2.46 1.53

For both the top and bottom panels, each column represents results from a separate instrumental variables

regression. Each row reports the sum of coefficients for a variable for different possible lag lengths. Not

reported are coefficients of month dummies and a time trend. Absolute value of z-statistics in parentheses. +

significant at 10%; * significant at 5%; ** significant at 1%

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