It’s a shocking statistic, but one that everybody knows: 70% of women are wearing the wrong size bra. Or is it eight out of ten women? Maybe it’s 90%. Either way, every article about bra fitting has to begin with the statement that most women don’t know their real bra size, before going on to explain how you find out your real size. Sometimes these articles, like this one by Rosie Johnston in today's Independent, also point out that wearing the wrong-sized bra can cause health problems.
Any woman reading an article about bra sizing reaps the twin benefits (sorry) of finding out how you really measure yourself for a bra as well as being told she’s superior to her less well-read sisters. So why is bra-size illiteracy still a problem? Is it because there just aren’t enough helpful articles about it?
Perhaps to find the answer, we need to go back to the source of the statistic – to the nine out of ten, or eight out of ten, or 75%, or whatever it is.
The only reported study I can find is one conducted by Wacoal in 2004 on 750 women. 750: is that a statistically significant sample size? Now, I’m no scientist, but I do know that a sample size needs to be a substantial proportion of the population you’re researching. Can we conclude that a study of 750 women gives us accurate information about all the women in the world?
Of course not, silly! When you’re using a sample size of 750 to draw conclusions about a population of approximately three billion, you have to take statistical error into account. The wise, science-minded writers at the Daily Mail, the Guardian and even the Times Higher Education Supplement have done this for us by taking 10% off Wacoal’s original statistic, turning “eight out of ten” into 70%.
For balance, the wise, science-minded writers at the Daily Mail also add 10%, turning eight out of ten into nine out of ten. The BBC demonstrates even greater journalistic integrity by seeking out a secondary source: a Bravissimo press release taking us back to 80%.
So there we have it: a statistic that offers very little in the way of support, although it has the charm of being heavily embroidered. Next time a national news source tells you that most women are incapable of choosing underwear to fit their own bodies, you might want to ask about the writer’s own ability to take accurate measurements.