First of all, the
number of abortions is an incorrect metric. One should look at the
rate of abortions compared to the number of births. This controls for changes in demographics and contraceptive use.
pregnancies = birth + abortions + miscarriages, but since miscarriage rate is low (< 1%) you can safely approximate that pregnancies = births + abortions. (Early pregnancies have >50% spontanous termination rate, but the woman usually does even not know she was pregnant, so we don’t count these.) The abortion rate is usually given us abortions/births, although technically it should be abortions/(abortions+births), as the latter is simply a probablity that a randomly chosen pregnancies will be aborted. Anyway, whichever way you use, the lesson here is to use relative numbers. Absolute numbers are largely useless (except for shock value).
That someone was me (hi

), and that was not what I suggested. The argument starts around here:
forums.catholic-questions.org/showthread.php?t=596167&page=8
What I was actually arguing is that after Poland outlawed abortion, while the neighboring countries did not,
Poland did not record the expected increase in number of births. I.e. if 20% of pregnancies were aborted pre-pan, then the birth rate should have jumped 20% post-ban – it did not, even worse:
it continued falling. (Technically, I was comparing fertility rates, i.e. number of children per woman, to control for demographic changes). Further down the thread, I controlled for % of Catholics, GDP per capita, sexual activity and contraceptive use – showing that none of these can be blamed for discrepancy and all countries used in the comparison are similar.
The fertility rate in Poland is about the same as in very similar neighboring countries – where 10-20% of pregnancies are aborted. All other factors being the same, this indicates that roughly 10-20% of pregnancies in Poland are aborted anyway, despite the ban. As St. Francis noted, the Polish abortion tourism is not apparent in the data, hence, these abortions are performed illegally in the country. (Anectodal experience gathered by me while living in Poland agrees here.)
Also, the long-term trend in abortion rate seems to be down. Probably has more to do with better contraceptives and better understanding of what abortion is, then actual legislation.
The abortion rate in the US, for example, peaked in 1984 (under Reagan) and has been declining ever since (under Bush I and Clinton) until 2007 or so (Bush II). Since then, it hovers around 20%. Abortion rates in European countries are generally below that and continue to fall.