If there is one person in the world who knows bras, it's Dr. Deidre McGhee.
McGhee runs Breast Research Australia at the University of Wollongong. She is also a sports physiotherapist, and taught women about breast support and bra fit for 15 years before before becoming a researcher. McGhee claims that 85% of women are wearing the wrong size bra, and that fashion is usually valued over function.
It's absolutely amazing there are so many women in the wrong sized bra. If it was men and underpants it wouldn't be the case.
Breast Research Australia developed an app called Sports Bra to help women find a bra that fits them.