Silicon Valley companies are making news these days for their efforts to fix the underrepresentation of women in tech. Many are focused on increasing the pipeline of women studying STEM in high school and college. But pipeline factors are not the only reason for the low numbers of women: Companies are failing to retain the female employees they have. A study by Jennifer Glass and coauthors in 2013 found that women leave STEM fields at dramatically higher rates than women in other occupations. After 12 years, 50% of technical women, predominately in engineering and computer science, had switched to other fields; 20% of other women professionals had done the same.