New research by two economists, Stephen J. Rose and Heidi Hartmann, shows that traditional measures have overstated what women earn over time. They challenge the belief that the gender wage gap has decreased because traditional measures track only those women who work full time for a full year - which is only about half of working women in any single year. When they studied actual earning histories they found that women on average earned only 38 percent of what men did.
See "Still a Gender Wage Gap", Jeff Madrick, The New York Times, June 9, 2004