In recent years it's been fashionable for conservatives and libertarians to tout "research" showing that the gender wage gapthe observed difference in pay between men and womenis supposedly due to women not wanting to work nearly as much, perhaps because of family demands. To some extent, even if this research was accurate, it isn't very satisfying: the question then becomes why women necessarily have to sacrifice their careers to raise a family. Why can't the fathers pitch in too? Why can't employers be more accommodating? Why don't we have paid family leave? And so on and so forth. Nevertheless, perhaps the research isn't accurate, and discrimination is in fact alive and well. A pair of sociologists at Cornell recently designed an experiment suggesting that, contrary to the libertarian line, employers may well actively discriminate against mothers:
[W]e conducted a laboratory experiment in which participants evaluated application materials for a pair of same race, same gender, ostensibly real job applicants who were equally qualified but differed on parental status. The results strongly support the discrimination hypotheses. Relative to other kinds of applicants, mothers were rated as less competent, less committed, less suitable for hire, promotion, and management training, and deserving of lower salaries. Mothers were also held to higher performance and punctuality standards. Men were not penalized for being a parent, and in fact, appeared to benefit from having children on some measures.
Add that to the research showing that pregnancy discrimination is very much alive and kicking. For more on the gender wage gap, Alas, a Blog ran a pretty comprehensive series on the subject awhile back that's worth reading.