Only by ignoring crucial factors related to compensation such as education, experience, and field of employment can you find a wage gap. Second, the gap lags behind current behavior. Women's average earnings today reflect the educational and career choices they made years and even decades ago. Today women are earning more than half of all college degrees and nearly half of all graduate degrees. Many of these women will earn higher salaries than their mothers, if they choose to pursue higher-paying fields.
Personal choices have a strong effect on our earnings.
In the office where I work, one employee leaves in the mid-afternoon so that she can be home with her children after school. For her, time spent with family is far more valuable than the additional money she would earn from working those few extra hours every day. A wage gap certainly exists between her and her coworkers, but it is not one caused by discrimination. Another woman I know left a lucrative job in the public relations department of a large corporation to start her own business. She took a pay cut, which contributed to the lower average earnings of all women, but she is far happier as an entrepreneur than she was as a cog in a corporate machine.