The WaPo explains:
Lydia McGrew questions whether 98 percent of Catholic women have actually used contraceptives, a figure that became ubiquitous in last week’s birth control debate. She parses the research behind the stat, which comes from a 2011 Guttmacher Institute study:
The survey was limited to women between 15-44. Ah, well, that explains how we weren’t including the elderly, but it also means that the silly “percent of all Catholic women” thing should be chucked out right from the beginning. More strikingly…it excluded any women who were a) not sexually active, where that is defined as having had sexual intercourse in the past three months (there go all the nuns), b) postpartum, c) pregnant, or d) trying to get pregnant! In other words, the study was specifically designed to include only women for whom a pregnancy would be unintended and who are “at risk” of becoming pregnant…a statistic based on a study that explicitly excluded those who have no use for contraception is obviously irrelevant to a question about the percentage of Catholic women who have a use for contraception.
I called up Rachel Jones, the lead author of this study, to have her walk me through the research. She agrees that her study results do not speak to all Catholic women. Rather, they speak to a specific demographic: women between 15- and 44-years-old, who have been sexually active and who are not attempting to become pregnant.
“If we had included women up to age 89, we would have probably found a lower proportion had ever used artificial contraception,” said Jones. “But the policies being implemented right now are ones that don’t effect them. Right here and now, we’ve got 98 percent who have ever used a contraceptive method, who are not attempting to get pregnant. Those are who will be impacted by this.”
Jones’s study does not find that 98 percent of all Catholic women have used contraceptives. What it does, however, bear out is the claim that many have made with this statistic: that sexually-active, Catholic women do tend to use contraceptives at the same rate as their non-Catholic counterparts. On that front, Jones looked at women who had been sexually active within the past three months. You can see the results of that question in the chart above, where contraceptive use of Catholics look virtually identical to those of all women.
Check the link for more.