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Di Xu

Di Xu, Florence Xiaotao Ran.

Using data with detailed instructor employment information from a state college system, this study examines disciplinary variations in the characteristics and effects of non-tenure-track faculty hired through temporary and long-term employment. We identify substantial differences in the demographic and employment characteristics between the two types of non-tenure-line faculty, where the differences are most pronounced in STEM fields at four-year colleges. Using an instrumental variables strategy to address student sorting, our analyses indicate that taking introductory courses with temporary adjuncts reduces subsequent interest, and the effects are particularly large in STEM fields at four-year colleges. Long-term non-tenure faculty are generally comparable to tenure-track faculty in student subsequent interest, but tenure-track faculty are associated with better subsequent performance in a handful of fields.

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Vivian Yuen Ting Liu, Di Xu.

Nationally, 15% of first-time community college students were high school dual enrollment (DE) students, which raises concerns about how high school peers might influence college enrollees. Using administrative data from a large state community college system, we examine whether being exposed to a higher percentage of DE peers in entry-level (gateway) math and English courses influences non-DE enrollees’ performance. Using a two-way fixed effects model, our results indicate that college enrollees exposed to a higher proportion of DE peers had lower pass rates and grades in gateway courses, and higher course repetition rates. Supplemental student-level analysis suggests that greater exposure to DE peers during a student’s initial semester in college reduces next-term college persistence.

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Di Xu, Qing Zhang, Xuehan Zhou.

This paper presents new experimental estimates of the impact of low-ability peers on own outcomes using nationally representative data from China. We exploit the random assignment of students to junior high school classrooms and find that the proportion of low-ability peers, defined as having been retained during primary school (“repeaters”), has negative effects on non-repeaters’ cognitive and non-cognitive outcomes. An exploration of the mechanisms shows that a larger proportion of repeater peers is associated with reduced after-school study time. The negative effects are driven by male repeaters and are more pronounced among students with less strict parental monitoring at home.

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