I get the impression that some, if not many of of our users think that condom failure rates are the same as condom breakage/slippage rates. In other words, think that when we explain that in typical use, condoms are 85% effective, that means that 15% of condoms break.
It doesn't: that is NOT what those rates mean. I hate for anyone to be presuming it is and to panic about a potential pregnancy via condom use because of that misunderstanding.
When we say condoms are effective 98% of the time in perfect use, that means that 2% of women using condoms (or, 2 out of every 100) as a sole method perfectly -- as in, following all the directions, including proper storage of condoms -- each year become pregnant. When we say they are 85% effective in typical use -- the way most people use them, which includes storing them incorrectly, putting them on wrong or too late or not using them at all -- that means 15% of women using them that way become pregnant in one year. People often forget that typical use rates for any method include people who really just aren't using that method: that some people who, when asked, say condoms are what they use as a method, have times when they simply aren't used, period. Same with typical use rates for the pill and other methods.
But condoms actually don't break very often, particularly when used perfectly. Here are a few quotes on that for you (bolding mine):
"Condoms hardly ever break if they are stored and used correctly. Studies show that latex condoms break only about 0.4% (4 out of 1000) of the time during the first five uses, and polyurethane condoms break 4% (4 out of 100) of the time during the first five uses." - http://www.youngwomenshealth.org/malecontraceptives1.html
"Men attending 3 sexually transmissible disease clinics and a university health service in Sydney were given a questionnaire asking how many condoms they had used in the past year and how many broke during application or use or slipped off. Respondents were 544 men aged 18 to 54 years. Of these, 402 men reported using 13,691 condoms for vaginal or anal intercourse; 7.3% reportedly broke during application or use and 4.4% slipped off. Men having sex with men reported slightly higher slippage rates than those having sex with women. Breakage and slippage were unevenly distributed among the sample: a few men experienced very high failure rates. A volunteer subsample reported 3 months later on condoms supplied to them: 36 men used 529 condoms, of which 2.8% broke during application or use and 3.4% slipped off. Many of these failures pose no risk to the user, especially those occurring during application, as long as they are noticed at the time, but failure may discourage future use." - from http://www.ncbi.nlm.nih.gov/pubmed/8476971
"In an effort to define condom performance in a group of monogamous couples typical of those using condoms for contraception, we conducted a clinical trial of a single brand of lubricated condoms (Durex Ramses). A total of 4637 attempts to use the condom were evaluated. Six breaks occurred before intercourse (nonclinical breaks), and 10 condoms broke during intercourse or were only noted to have broken upon withdrawal (clinical breaks), resulting in a nonclinical breakage rate of 0.13% (95% confidence interval, 0.05-0.28%), clinical breakage rate of 0.28% (0.15-0.48%), and a total breakage rate of 0.41% (0.25-0.64%). The rate of complete slippage was 0.63% (0.42-0.90%), and total failure (clinical breaks plus complete slips) was 1.04% (0.76-1.37%)." - from http://www.ncbi.nlm.nih.gov/pubmed/9306027
In other words, the rate of breakage/slippage is far, FAR lower than many think or assume, and is a much different figure than rates of effectiveness in typical or perfect use. A condom can break or slip off in EITHER kind of use, and is much more likely to with imperfect use, yet still, breaks and total slip-offs are actually pretty rare.
Want to be sure you're using condoms properly? Check it out: Condom Basics: A User's Manual. Remember that when it comes to preventing pregnancy from a condom failure, the key is using them correctly AND consistently: from start to finish, every time you have intercourse.