The Indirect Effects of Educational Expansions: Evidence from a Large Enrollment Increase in University Majors
利用意大利STEM专业扩招的数据，研究发现扩招导致同班同学准备不足和教学资源拥挤，降低了原有学生的学习效果，但若新同学提升了班级平均准备水平，学习效果反而提高。
Increasing access to education may have consequences that go beyond effects on marginal students encouraged to enroll. It may change peer effects, school quality, and returns to skill. This paper studies how classmates and teaching inputs affect learning of university students, exploiting an educational expansion in Italian STEM majors. Newly collected data on 27, 236 students indicate that less prepared classmates and congestion of teaching resources lowered learning of incumbent students in STEM fields. Their learning, however, increased in courses in which the new classmates raised average preparedness. These effects might have had long-lasting consequences on the returns to STEM degrees.