I have often heard the statistic that 1/3 of pregnancies end in abortion. I wanted to see where those statistics came from.
I found one study that describes data as such:
“The national legal induced abortion ratio increased from 196 per 1,000 live births in 1973 (the first year that 52 areas reported) to 358 per 1,000 live births in 1979 and remained nearly stable through 1981 (Figure 1) (Table 2). The ratio peaked at 364 per 1,000 live births in 1984 and since then has shown a nearly steady decline. In 2000, the abortion ratio was 245 per 1,000 live births in 49 reporting areas and 246 for the same 48 reporting areas available for 1999. This represents a 3.8% decrease from 1999 (256 per 1,000 live births) for the 48 reporting areas”
It appears to me that the statitistic of 1/3 of pregancies would come from the 1984 statistic of 364 per 1000 live births. However, it would be important in this case to also account for natural pregnancy loss (e.g. miscarriage, stillbirth). At a maximum, I would characterize the %of pregnancies ending in abortion as such:
Abortion rate = (364 Abortions) / (364 Abortions + 1000 Live Births + X Miscarriages + Y Stillborn births)
In which case, if we assume that X and Y are zero, which they’re not, the maximum fraction of pregnancies ending in abortion would be (occurring in 1984):
(364)/(364+1000+0+0) = 26.6% (approximately 1 in 4)
Using recent statistics, the rate of pregnancy loss is derived as such:
4,058,000 live births
1,995,840 pregnancy losses
=492 pregnancy losses/1000 live birth.
That would bring the 1984 statistic to
(364)/(364+1000+492) = 19.6% (approximately 1 in 5)
Recent data (from the study cited above) indicates that the 2000 rate of abortion is 246/1000 live births. Given constant pregnancy loss rates, that implies that the year 2000 fraction of pregnancies ending in abortion is:
246/(246+1000+492) = 14.2% (approximately 1 in 7).
That’s nevertheless unacceptable. However, I think that in order to be credible, pro-life groups need to use the latest statistical data.
My little back-of-the-envelope statistics certainly are rough, but it seems to me that the 1/3 statistic needs to be updated.