The average American woman today owns six bras, one of which is a strapless bra, and one in a color other than white. While reliable data are hard to obtain, it is thought that in the Western world about 90% of women wear bras. Some women wear bras based on modesty; others because they believe that it is part of their cultural norm and that not wearing a bra would lead to ostracism.
Bras are a relatively recent invention and are by no means universally worn around the world. In a cross-cultural study of bra size and cancer in 9,000 in the 1960s, a Harvard group found 93% of women wore bras (from 88% in the UK to 99% in Greece), but could not find enough women in Japan with bras to complete their study. In a number of cultures, women are quite comfortable to sunbathe or swim without any external support.
The prevalence of the bra, and perceived social expectation to wear one, does not imply that openly displaying it is encouraged. On the contrary, it is often not considered suitable to expose one's brassiere in public in western cultures, even partially, despite the fact that it is similar in appearance to the upper part of a bikini; to do so may be considered sexually provocative. However more young people are doing so, and bra straps are a common sight. Occasionally they may wear a bra as outerwear. An attractive bra can be considered partly as an accessory, just as a camisole might; more women, particularly in Eastern Europe, are now wearing translucent tops which reveal the underlying bra.
Even considering this relative cultural taboo, being seen in one's bra is still more socially acceptable than exposing the bare breasts, except at the beach. Indeed, women may choose to be seen in just a bra to make a specific point. For instance, bras have recently been used by organizations like breast cancer charities to raise money, either by sponsored walks or to sell bras owned or decorated by celebrities.
An increasing number of women and health professionals are challenging the traditional values that suggest that that bras are either medically necessary or required socially and are adopting bralessness (also known as bra freedom, or breast freedom). One survey found that 20% of women over 50 were not wearing bras (Farell-Beck and Gau p.171).
Some men also choose to wear bras. This may because they have large breasts due to a condition known as gynecomastia or simply obesity.
Many entertainers, actresses and members of the fashion industry have chosen not to wear bras. Susan Stranks who presented the Thames TV children's programme, Magpie between 1968 and 1974 chose not to wear a bra, even on camera. Another well known woman who regularly appears braless on TV is the presenter of BBC Gardening's Ground Force, Charlie Dimmock.