A new Catalyst research study reports that the number of female leaders on the boards of Fortune 500 companies is increasing slowly -- but surely. Between 2001 and 2003, the percentage of corporate director seats held by women rose from 9.5% to 13.6%.

If the current rate of increase continues, women will hold a quarter of all board seats in, well, 20 years. Looks like the Fortune 500 has a way to go. It's good to see that more than 50 of companies listed claim 25% female directors, but it's disheartening that an equal number seat none.