According to a 2012 report by the National Shoe Retailers Association, the average American woman's shoe size is between size 8 1/2 and 9. This is a worldwide trend, as a 2012 British report found that the average British woman wears a British size 6, or U.S. size 8 shoe.
Women's shoe sizes have been increasing since the beginning of the 20th century. This seems to correspond with the increase in the average female height and weight throughout that time period. Experts also theorize that this growth may have something to do with processed food consumption stimulating growth hormone production. Taller women tend to have larger feet.