Understanding Variation in Estimates of Diversionary Effects of Community College Entrance: A Systematic Review and Meta-analysis

Abstract

Decades of research have estimated the effect of entering a community college on bachelor's degree attainment. In this study, we examined the influence of methodological choices, including sample restrictions and identification strategies, on estimated effects from studies published between 1970 and 2017. After systematically reviewing the literature, we leveraged meta-analysis to assess average estimates and examine the role of moderators. In our preferred model, entering a community college was associated with a 23-percentage-point decrease in the probability of baccalaureate attainment, on average, compared with entering a four-year college. The size of effects appeared to grow over the past three decades, though this coincides with substantial shifts in the college-going population. Methodological choices, particularly how researchers define the treatment group, explain some variation in estimates across studies. We conclude with a discussion of the implications for future inquiry and for policy.

Keywords: bachelor’s degree attainment; community college transfer; community colleges; diversionary effect; higher education; meta-analysis.

Figure 1.

Average risk difference for groups of studies based on methodological choices. Note: Estimates are drawn from an ordinary least squares regression analysis performed on the full sample of studies (see Table S3, column 1, in the online appendix). The no controls estimates include effect sizes that simply compare the means for baccalaureate attainment of community college and four-year college entrants; controls includes effect sizes from analyses that use statistical controls. The left-hand panel shows effect sizes among studies that capture all community college entrants in the treatment group; the right-hand panel shows studies that restrict the treatment group to community college entrants who transferred to a four-year college (some of those studies ensure students in the treatment and control groups entered college at the same time; others do not match based on entry cohort).

Figure 2.

Forest plot: Best-evidence sample. Note: The figure presents the unadjusted risk difference with 95 percent confidence intervals from each effect size in the best-evidence sample, ordered by year of college entry.

Figure 3.

Scatterplot of predicted risk difference by year students began college: Best-evidence sample. Note: The scatterplot presents adjusted estimates of risk difference for each effect size, obtained from the final model performed on the best-evidence sample (Table 4, Model 3).