that tries to quantify the effect:
Thomas Stratmann, who, with law professor Jonathan Klick, has pushed the idea of the rational teenage sex drive. Their hypothesis is that if teenagers really did think about the consequences of their actions, they would have less risky sex if the cost of risky sex went up. They discovered a very specific source of that higher risk: "In some states, there are abortion-notification or -consent laws, which mean that teenagers can't get an abortion without at least one parent being informed or giving consent." If teenagers are rational, such laws would discourage risky sex among teens, relative to adults.The abstract says:
Klick and Stratmann claim to have found evidence of exactly this. Wherever and whenever abortion-notification laws have been passed, gonorrhoea rates in the teenage and adult populations start to diverge. When it becomes more troublesome to get an abortion, teenagers seem to cut back on unprotected sex.
Using gonorrhea rates among older women to control for unobserved heterogeneity across states, our results indicate that the enactment of parental involvement laws significantly reduces risky sexual activity among teenage girls. We estimate reductions in gonorrhea rates of 20 percent for Hispanics and 12 percent for whites.There will be plenty of opposition to Prop. 85, as it failed before, but I haven't seen anyone explain any empirical evidence of harm.