Is the falling abortion rate due solely to fewer women becoming pregnant?

I’m somewhat skeptical of the Guttmacher Institute’s latest estimates for annual abortion numbers because of the large number of abortion providers which didn’t respond to them.  Regardless, some abortion advocates have attempted to argue that a decline in pregnancies is close to the only cause of the decline in abortion rate.

For example, Libby Anne argues: 

It’s particularly interesting to note that the abortion rate fell during this period, even as the birth rate fell. In other words, the falling abortion rate wasn’t the result of more women choosing parenthood and the falling birth rate isn’t a result of more women having abortions. Instead, both are the result of a third external factor—fewer pregnancies.

The problem is she does no number crunching.  The birth rate is falling alongside the abortion rate.  Okay.  But are they falling in tandem?  

According to the Guttmacher Institute, abortion rates fell 13% from 2008 (1.21 million and a rate of 19.4) to 2011 (1.06 million and a rate of 16.9) with there being 150,000 fewer abortions a year. 

According to the CDC, fertility rates (which are based number of births by 1,000 women aged 15-44) fell 7.2% from 68.1 in 2008 to 63.2 in 2011.  There were 294,104 fewer births in 2011 (3,953,590) than in 2008 (4,247,694).

That would mean there were approximately 450,000 fewer pregnancies which were ended either by birth or abortion in 2011 than in 2008. 

In 2008, the abortion ratio (abortions per 1000 births in the same age group) was 285.  In 2011, it’s 268.   That’s a 6% decline. 

Now maybe that decline is solely caused by a subset of women who would have had abortions if they became pregnant doing things to prevent pregnancy.  But then that argument has to be made.

The problem with making it is the abortion ratio for the non-existent pregnancies in 2011 vs. 2008 (150K abortions/294,104 births) is 510.  That’s a higher number than the CDC has for the 2010 abortion ratio of sub-groups of women who have very high abortion ratios.  For example, according to the CDC, the abortion ratio of 16-year-olds in 2010 was 394.

The CDC’s abortion ratio only goes above 510 for 15-year-olds (541) and girls younger than 15 (837). 

So while it’s true that a good percentage of the abortion decrease is based on fewer pregnancies (based on abortion ratio numbers, I would estimate at least half), that’s not the whole story for the abortion decrease.