The basic logic of the Roe Effect is thus:
1. Those who favor legal abortion are much more likely to have the procedure than those who oppose it.
2. Children usually follow their parents’ political leanings.
3. Therefore, pro-choice parents will have more abortions.
4. Therefore, pro-choice parents will have fewer children.
5. Therefore, the pro-choice population gradually shrinks in proportion to the pro-life population.
6. Therefore, support for legal abortions will decline over time.
The logical failing is 3 -> 4, which simply does not follow. Yes, all else being equal, people who have more abortions will have fewer children, but all else is not equal in the real world. If the high-abortion group has higher fertility for other reasons, it will out-breed the low-abortion group. Within both groups, those who behave identically to the group but have more or less abortions will also be increasing in size, but this increase may be less than the increase of the high-abortion over the low-abortion group. There are currently two reproductive strategies proving to be successful:
(1) a strategy associated with socially conservative values, including a high commitment to the bearing of children within marriage; and
(2) a strategy associated with antisocial behavior, early sexual experimentation, a variety of sexual partners, low educational attainment, low commitment to marriage, haphazard pregnancies, and indifference to politics.
The former is the low-abortion group, the later is the high-abortion group. Who’s winning? Hard to say.
More fundamentally, the Roe effect conflates a strong feeling against personally getting an abortion with a strong feeling that this should be law. Suppose people who don’t get abortions outbreed those who do. If it’s anything like America, these groups also have a lot of other disagreements and resentments unrelated to abortion. When the anti-abortion group reaches 51%, it will have to ask itself “hey, should we obviate our own reproductive advantage?” The future belongs to those who show up, and they might not want to drag the rest of us there with them.