The Volokh Conspiracy - According to new study, access to a computer at home appears to CAUSE rape.

According to the headlines on the internet, a new study by Todd Kendall of Clemson University (using regression analyses of panel data) finds that having computer access to the internet at home, and thus better access to internet porn, is consistent with the hypothesis that more porn REDUCES the incidence of rape (tip to Instapundit).

What neither the author of the study nor online commentators seem to have noticed is that the data also are consistent with the hypothesis that owning a computer INCREASES the incidence of rape. Indeed, the observed rape increasing effect of computer access is even more highly significant than the observed rape decreasing effect of internet access (p. 43).

Since by 2003 87% of households with computers had access to the internet, and since the two effects are about even in size, the "rape reducing" effects of internet access (-.730, p. 43) are almost completely offset by the "rape increasing" effects of owning a computer (.641, p. 43). Since it appears that everyone in the study who lived in a household with computer internet access also lived in a household with a computer, the net effect on rape of having household access to a computer and household access to the internet was nearly zero and probably not even close to being significant.

The supposed rape reducing effect of internet access that the study and commentators are talking about is the effect of household internet access, CONTROLLING for the observed rape inducing effect of household computer access. That these two highly intercorrelated variables tend to have implausible offsetting effects when significant is supported by other models in Kendall's paper; for example, one model shows a huge increase in prostitution arrests associated with computer access and a huge offsetting drop in prostitution arrests associated with internet access (p.51).

Without noting that internet and computer access go together and that the observed effects seemingly offset each other, one might wrongly conclude (as Todd Kendall appears to do) that his reported regression analyses of rape are consistent with the hypothesis that internet access reduces the measured incidence of rape. IMO, he should rerun his analyses using his internet access variable WITHOUT including the variable computer access, and then post all the coefficients in his main models. I would be interested in seeing those results.

It is amazing how many scholarly papers I've read in the last year either fail to report, misreport, or misleadingly present the use of control variables.

Just to be clear, the title of this post is tongue-in-cheek. Just from Kendall's regression analyses, I am skeptical of any meaningful effect one way or the other.

UPDATE: There are some excellent comments below, and a few that don't fully understand the main problem with the Kendall study. Although it is possible to have a 10% increase in internet access without ANY increase in computer access, that is extraordinarily unlikely.

Since by 2003 about 87% of those with computer access have internet access, what would be the likely effect on the incidence of rape of a state having a 10% increase in computer access and a corresponding 8.7% increase in internet access? One would multiply .641 by 10 and add it to -.730 multiplied by 8.7. The result would be an insignificant INCREASE in the incidence of rape. With different assumptions, one can get a slightly different net result, but there is no plausible combination that should lead to an overall effect that significantly reduced or increased the incidence of rape.

	[Jim Lindgren, October 31, 2006 at 12:42am] Trackbacks According to new study, access to a computer at home appears to CAUSE rape. According to the headlines on the internet, a new study by Todd Kendall of Clemson University (using regression analyses of panel data) finds that having computer access to the internet at home, and thus better access to internet porn, is consistent with the hypothesis that more porn REDUCES the incidence of rape (tip to Instapundit). What neither the author of the study nor online commentators seem to have noticed is that the data also are consistent with the hypothesis that owning a computer INCREASES the incidence of rape. Indeed, the observed rape increasing effect of computer access is even more highly significant than the observed rape decreasing effect of internet access (p. 43). Since by 2003 87% of households with computers had access to the internet, and since the two effects are about even in size, the "rape reducing" effects of internet access (-.730, p. 43) are almost completely offset by the "rape increasing" effects of owning a computer (.641, p. 43). Since it appears that everyone in the study who lived in a household with computer internet access also lived in a household with a computer, the net effect on rape of having household access to a computer and household access to the internet was nearly zero and probably not even close to being significant. The supposed rape reducing effect of internet access that the study and commentators are talking about is the effect of household internet access, CONTROLLING for the observed rape inducing effect of household computer access. That these two highly intercorrelated variables tend to have implausible offsetting effects when significant is supported by other models in Kendall's paper; for example, one model shows a huge increase in prostitution arrests associated with computer access and a huge offsetting drop in prostitution arrests associated with internet access (p.51). Without noting that internet and computer access go together and that the observed effects seemingly offset each other, one might wrongly conclude (as Todd Kendall appears to do) that his reported regression analyses of rape are consistent with the hypothesis that internet access reduces the measured incidence of rape. IMO, he should rerun his analyses using his internet access variable WITHOUT including the variable computer access, and then post all the coefficients in his main models. I would be interested in seeing those results. It is amazing how many scholarly papers I've read in the last year either fail to report, misreport, or misleadingly present the use of control variables. Just to be clear, the title of this post is tongue-in-cheek. Just from Kendall's regression analyses, I am skeptical of any meaningful effect one way or the other. UPDATE: There are some excellent comments below, and a few that don't fully understand the main problem with the Kendall study. Although it is possible to have a 10% increase in internet access without ANY increase in computer access, that is extraordinarily unlikely. Since by 2003 about 87% of those with computer access have internet access, what would be the likely effect on the incidence of rape of a state having a 10% increase in computer access and a corresponding 8.7% increase in internet access? One would multiply .641 by 10 and add it to -.730 multiplied by 8.7. The result would be an insignificant INCREASE in the incidence of rape. With different assumptions, one can get a slightly different net result, but there is no plausible combination that should lead to an overall effect that significantly reduced or increased the incidence of rape.