Wouldn't nutrition, diet, and lifestyle changes be a far more likely explination than evolution? What mechanism within the last 80 years could possibly be the driving factor behind evolutionary changes in peoples feet size? Its not like people in the 1930s were dieing due to overly large feet, nor has foot size been a significant factor in mating sucess. People are taller today too, but that isn't because tall people use to die more often or was once considered unattractive, it is mostly because of better nutrition thanks to far more varied and reliable diets.