Any given raw wage gap can be dissected into an "explained" part, due to differences in characteristics such as education, hours worked, work experience, and occupation, and/or an "unexplained" part, which is typically attributed to discrimination, differences not controlled for, individual choices, or a greater value placed on fringe benefits. This may be further explained when America takes into account that men are more likely to negotiate for higher pay. According to a study by Carnegie Mellon, when negotiating pay, 83% of men negotiated for a higher wage compared to the 58% of women who asked for more. Researchers say that women who do request either a raise or a higher starting salary are more likely than men to be penalized for those actions. Cornell University economists Francine Blau and Lawrence Kahn stated that while the overall size of the wage gap has decreased somewhat over time, the proportion of the gap that is unexplained by human capital variables is increasing.