Association for Public Policy Analysis & Management

We conduct a randomized field experiment to uncover the causal effect of summer enrollment on credit accumulation, student retention, transfer rates to four-year colleges, and graduation among community college students. We use a stratified randomization to assign 167 summer enrollment vouchers to 406 eligible students in two waves: the first during the Spring 2016 semester and the second during the Spring 2017 semester. We use this assignment as an instrumental variable in estimating the impact of summer enrollment on academic outcomes. The instrument is mechanically valid and highly relevant. The vouchers increase summer enrollment by 0.69 credits and increase enrollment rates by 22 percentage points. For every additional credit attempted during the Summer semester, students accumulate 0.81 additional completed credits that semester. Summer enrollment has a positive but not significant impact on accumulated credits during the three semesters after the Summer semester. There is no significant impact on grades. Summer semester grades decrease insignificantly as a result of the additional students, while grades during the subsequent semesters see insignificant increases as a result of summer enrollment.

Experimentally-induced summer enrollment significantly increases rates of associate degree attainment and rates of transfer to 4-year colleges. Treatment students are 7.1% more likely to graduate with an associate degree and 5.1% more likely to transfer to a four-year college. Summer enrollment has no significant impact on dropout rates. We find evidence that the increase in graduation rates results from vouchers enabling students to meet their target graduation plans, possibly due to the additional slack in academic plans. Students with sooner target graduation dates are marginally significantly more likely to utilize the assigned vouchers for summer enrollment. Summer students are then significantly more likely to meet target graduation plans.

We measure baseline economic and academic preferences for all students in our sample. Incentivized measures of preferences for summer enrollment are strong predictors of positive long-term outcomes, providing evidence for the role of enrollment preferences in academic achievement.