This is purely a curiosity based question, although I figure this could be useful in reevaluating whether I want to switch to a more effective contraception.
So I know that efficacy rates are determined over a period of one year through clinical study and surveys. But it seems that none of these studies extend one year of observation. So I went googling and found this article by the New York Times: https://www.nytimes.com/interactive/201 ... ncies.html
I read it and it seems that over ten years, the failure rates for typical use of barrier, behavioral, and most short term hormonal methods (like the pill or the patch) seem to skyrocket. For example, I have been on the combined pill for four years now, and I’m really good about taking it every day. I know that I have not missed a pill more than once or twice, and that was over three years ago (and I was also not sexually active at the time). So all in all, I’d like to consider myself a perfect user, or at least very close. But because you can never be sure and humans are not perfect, I recognize that it may be more beneficial to refer to the typical use rates to get a confident minimum efficacy rate. When looking at this article, for the pill, perfect use failures after four years of use remain 1 in 100, but typical use rates jump to 31 in 100, from the 9 in 100 from one year of use. Why is this? Where do they get their numbers? Is everyone guaranteed a higher risk of pregnancy after so long using certain contraceptions certain ways? How does combining methods factor into all this? How would calculate the efficacy of multiple methods after multiple years of use?
Thanks for your input!