3. Once students are off the STEM pathway, they cannot get back on it.

4. The culture of STEM fields is off-putting once higher education is reached.

5. The returns are insufficiently high to justify greater adherence to STEM fields.

He noted that his data are best suited to explore the last three of these explanations. Students started switching away from STEM majors in their very first semester, and the students most likely to leave STEM majors were the ones who took fewer STEM courses their first semester rather than more courses. Students who took more than 40 percent of their courses in STEM their first semester were much less likely to leave the major than students who took less than 40 percent of their courses in STEM fields. This observation holds for students in four-year colleges, students in two-year colleges, and high-ability students.

The relatively small number of students who converted to STEM majors also took relatively few STEM courses their first semester. This piece of evidence is “suggestive,” said Bettinger, that there might be some way of getting more non-STEM majors interested in those subjects—for example, by examining more closely the structure and conduct of introductory courses in STEM. However, STEM majors have extensive course requirements, and many courses typically must be taken in a particular order (that is, they have extensive prerequisites compared with other disciplines), which can make it difficult to switch into these majors.

The students who left STEM were just as likely to pass their initial STEM courses, so the difficulty of the courses did not seem to be the deciding factor. But the course demands of STEM majors are high and require commitment—even though, as Bettinger observed, some of the majors to which students switch, such as education, also have extensive course requirements, even if they are not as sequential as those for STEM majors.

THE CULTURE OF STEM FIELDS

Bettinger’s data also show that women were significantly less likely to stay in STEM fields, even among the top students, which suggests that the culture of STEM might have been a factor in their decisions. However, since the female students took STEM courses in high school and still expressed an interest in majoring in those subjects, the cultural problems would need to start or intensify in college for this explanation to hold.

According to Bettinger’s research, black students in four-year colleges were less likely to defect from STEM majors than other students, espe-



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