A survey published in the Harvard Business Review found that women who take a break from their careers for family or other reasons earn 18% less once they return to the workforce. This salary "penalty" may partly be the result of women returning to work in jobs with less responsibility, but it may also reflect women?s absence from the workforce during a time when many men are moving up the corporate ladder. The drop in pay becomes larger the longer women wait before returning to work.
See "Women Hit With Salary 'Penalty'", Los Angeles Times, February 23, 2005