Whlie doing some completely legitimate research for a thought-provoking academic project, I came across this online paper, which seems to show that liberalizing pornography laws is generally followed by decreases in the incidence of sex crimes in advanced societies (of course, the usual caveats about correlation not implying causation apply):
Within Japan itself, the dramatic increase in available pornography and sexually explicit materials is apparent to even a casual observer. This is concomitant with a general liberalization of restrictions on other sexual outlets as well. Also readily apparent from the information presented is that, over this period of change, sex crimes in every category, from rape to public indecency, sexual offenses from both ends of the criminal spectrum, significantly decreased in incidence.
Most significantly, despite the wide increase in availability of pornography to children, not only was there a decrease in sex crimes with juveniles as victims but the number of juvenile offenders also decreased significantly.
These findings are similar to, but are even more striking than, those reported with the rise of sexually explicit materials in Denmark, Sweden and West Germany. The findings from Europe were, in turn, more dramatic than those reported for the United States. Kutchinsky (1991) studied the situation in Denmark, Sweden, West Germany and the U.S.A. following the legalization or liberalization of the appropriate pornography laws in those countries. The first three countries mentioned, decriminalized the production and distribution of sexually explicit materials in 1969, 1970, and 1973 respectively....
Kutchinsky found (1991) that in Denmark and Sweden adult rapes increased only modestly and in West Germany not at all. In all three countries, nonviolent sex crimes decreased. The slight increase in Denmark and Sweden, was thought by some most probably due to increased reporting as a result of greater and increasing awareness among women and police of the rape problem (Kutchinsky, 1985b, pp. 323). In Japan too, over the two decades reviewed in the present study, there was also most probably an increasing likelihood of reporting which makes the decrease in sex crimes seen in Japan even more impressive.