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June 22, 2007

Abortion Question

No, this isn't one of the usual rants. Rather, a question about statistics.

A third of women use an abortion service at some point in their life.

Now most will read that as one third of women will have an abortion (I am assuming that this number does not include those who consult an abortion service and then decide not to have one) at some point in their lives.

How is this figure actually arrived at? Is it actually by counting, or by survey? Or is it a more simple measurement: like, there are x numbers of abortions and y numbers of women of fertile age, y being three times x, so therefore one third of women have abortions?

The problem with that latter, simple, method being that there's a certain amount of double counting going on. For there are women who, over a lifetime, have more than one abortion.

So how is this number arrived at? Is it true that one third of women have an abortion or is it that there are enough abortions for one third of women to have one each?

June 22, 2007 in Health Care | Permalink

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Comments

It doesn't seem obviously wrong. On average for any age group between 15 and 44, there are about 400,000 women. Last year there were 200,000 abortions, of which 2/3rds were 1st time abortions. That means 166,000 first time abortions, over 400,000 women, which is 1/3rd.

It could be overstated if there are a lot of foreigners who come to Britain, I suppose.

Tim adds: "That means 166,000 first time abortions, over 400,000 women, which is 1/3rd."

I'm not getting this. The group is 29 years times the cohort of women, isn't it?

Posted by: Matthew | Jun 22, 2007 10:28:45 AM

Two-thirds of 200,000 is 133,333, but the answer is still correct.

Tim, think about it, if (by a sheer coincidence) that ALL women who had abortions were (say) 20 years old, then one-third of women 20 or over would have had at least one abortion.

Sure, you can time 400,000 women by 29, but you'd have to times 200,000 by 29 as well.

Posted by: Mark Wadsworth | Jun 22, 2007 11:02:15 AM

Here's the stats:

http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsStatistics/DH_075697

In 2006, for women resident in England and Wales:

* the total number of abortions was 193,700, compared with 186,400 in 2005, a rise of 3.9%
* the age-standardised abortion rate was 18.3 per 1,000 resident women aged 15-44, compared with 17.8 in 2005
* the abortion rate was highest at 35 per 1,000, for women age 19.
* the under-16 abortion rate was 3.9 and the under-18 rate was 18.2 per 1,000 women, both higher than in 2005
* 87% of abortions were funded by the NHS; of these, just over half (55%) took place in the independent sector under NHS contract
* 89% of abortions were carried out at under 13 weeks gestation; 68% were at under 10 weeks
* medical abortions accounted for 30% of the total compared with 24% in 2005
* 2,000 abortions (1%) were under ground E, risk that the child would be born handicapped

Non-residents:

in 2006 there were 7,400 abortions for non-residents carried out in hospitals and clinics in England and Wales (7,900 in 2005)

Posted by: Gary Marshall | Jun 22, 2007 11:10:25 AM

Yes, sorry, 133,000. But as Mark says can think of a first time abortion happening at any age from 15 to 44 (or whatever), at any time between Date of Birth + 15 and Date of Birth + 44. Or you can simplify things by just saying they all happen at an age, say 20.

Obviously there are nuances due to no. of abortions and no.of women, but if you look at the statistics they have been 175,000 plus for a long time, the number of women has been falling (by and large) and the no.of foreigners has been falling to (I assume this was because other European countries (or something to do with Ireland) didn't legalise abortion until a bit later).

Posted by: Matthew | Jun 22, 2007 11:10:43 AM

Or if you want to put it another way, there are 12.1m women of age 15-44 at present. If 0.133m have an abortion for the first time every year, that's just over 1%. Over 29 years that would be about 33%.

Posted by: Matthew | Jun 22, 2007 11:15:32 AM

OK, I'm getting confused here. If there were 670,000 live births in 2006 (which there were), then okay, 200,000ish abortions means that out of nearly 900,000 pregnancies, just over one in five were terminated. Surely that means 1 in 5 women who get pregnant have an abortion, not 1 in 5 of the entire fertile female population?

I was never good at sums and now I've got a sore head.

Posted by: Gary Marshall | Jun 22, 2007 11:17:38 AM


I haven't been able to find anything for the UK (in 5 minutes). The following is the abstract of a study from Australia.


Prevalence of induced abortion in a reproductive lifetime.

Chan A, Keane RJ.

Pregnancy Outcome Unit, Department of Human Services, Adelaide, South Australia. Annabelle.Chan@dhs.sa.gov.au

The period total first abortion rate (TFAR) has been used to estimate the proportion of women who will experience an induced abortion in their reproductive lifetime. It is a hypothetical measure as age-specific rates currently existing will change with time. Instead, a cohort TFAR has been calculated for women born around 1955 using legal-abortion reports in South Australia to calculate first abortion rates for each year of age from 15 years to 44 years for 1971-2000, respectively, and summing these. Yearly fertility rates were also calculated for this cohort to further describe their reproductive experience. Yearly first abortion rates were also calculated for later cohorts born in 1960-1980. The 1955 cohort TFAR was 288.1 per 1,000 women aged 15-44 years. Cumulative first abortion rates at specific ages were higher for subsequent cohorts (e.g., 309.6 per 1,000 at age 40 years for the 1960 cohort). Thus, about 29% of South Australian women born around 1955 and exposed to legal abortion throughout their reproductive lifetime experienced an induced abortion. This proportion would be higher for later cohorts of women born in 1960-1980 (e.g., at least 31% for those born in 1960).

Posted by: james C | Jun 22, 2007 11:31:20 AM

"Surely that means 1 in 5 women who get pregnant have an abortion, not 1 in 5 of the entire fertile female population?"

You're forgetting this is over a lifetime. If there are 12.1m women of reproductive age at any one time (this obviously varies a bit), and 900,000 pregnancies, then that's about 7.5% of (reproductive age) women in any one year are pregnant. Of those 1/5th have an abortion, which is about 1.5% of all reproductive women. Of this 2/3rds, or about 1% of all reproductive age women, are having an abortion for the first time.

But there are 29 years of this, from age 15 to 44.

Posted by: Matthew | Jun 22, 2007 11:38:39 AM

Sorry Matthew, I'm really trying to understand this and I'm failing dismally. I'm quite sure you're right :)

Posted by: Gary Marshall | Jun 22, 2007 11:53:49 AM

Gary M, nice try.

Do not forget that we reduced the number of abortions from 200,000 to 133,333 to account for second and subsequent abortions.

In the same way, let's assume that women who have babies have an average of two babies each, i.e. half of children born each year are a second child.

So you can knock your figure of 670,000 down by half to 335,000. Add back 133,333 from above, that's 468,333.

133,333 over 468,333 is 28%, not far off the one-third figure we started off with.

Posted by: Mark Wadsworth | Jun 22, 2007 12:05:12 PM

Gary - i can't really do better than Mark's original.

Imagine a world in which 1/3rd of women have abortions, but bizarrely they all have them on their 20th birthdays. Then as there are about 400,000 women who celebrate their 20th birthdays every year, then that would mean there was 133,000 abortions every year. In reality, of course, women have abortions at different ages, but the numbers wouldn't be different.

Posted by: Matthew | Jun 22, 2007 2:08:03 PM