Although many women begin their studies in these fields, their numbers drop at every stage of educational and professional advancement. At the undergraduate level in the U.S., about half of all students are women. Yet in the fields of science, technology, engineering and math—STEM for short—women account for only 39 percent of bachelor's degrees and 35 percent of Ph.D.s. At the end of this leaky educational pipeline, only 27 percent of the people working in STEM-related occupations are women.