A recent study by the American Association of University Women (AAUW) found that women's choices (their college major, occupation and hours at work) account for about two-thirds of the pay gap between women and men. The remaining third, researchers say, comes down to bias and discrimination in the workplace. According to the study, "women are still expected to be 'nice,' and women who negotiate for a higher salary can be perceived negatively." Some evidence even indicates that employers tend to penalize women more than men for initiating negotiations. Consider taking a salary negotiation workshop such as $tart $mart to toughen up.