Why women earn less: Just two factors explain post-PhD pay gap

Helen Shen:

Women earn nearly one-third less than men within a year of completing a PhD in a science, technology, engineering or mathematics (STEM) field, suggests an analysis of roughly 1,200 US graduates.

Much of the pay gap, the study found, came down to a tendency for women to graduate in less-lucrative academic fields — such as biology and chemistry, which are known to lead to lower post-PhD earnings than comparatively industry-friendly fields, such as engineering and mathematics.

But after controlling for differences in academic field, the researchers found that women still lagged men by 11% in first-year earnings. That difference, they say, was explained entirely by the finding that married women with children earned less than men. Married men with children, on the other hand, saw no disadvantage in earnings.

Many studies have reported similar gender pay gaps and have identified similar contributing factors — but few have systematically broken down the relative contributions of different variables, says Bruce Weinberg, an economist at the Ohio State University in Columbus who led the study, published in the May issue of American Economic Review1. “I was quite surprised that we could explain the wage gap using just field of study and family structure,” he says.