IF fewer children are being born AND sales of contraceptives are not up THEN less sex is being had. I don't see how it is possible to argue against that.

Hormonal birth control? Environmental factors reducing births?

Again: We talk about short term affairs -- both of these cases would be visible in VD statistics.

Also note the additional obvious problems: Other birth control sales, just like condoms, are easy to find statistically -- and environmental factors ought to be obvious among people trying to get kids.

It really strains credulity to think that Japanese people are going at it like bunnies but are simply light years ahead of everybody else on the planet in terms of sexual sophistication (to the point where unprotected anonymous sex is actually safe sex).