With rapid technological transformations to the labor market along with COVID-19 related economic disruptions, many working adults return to college to obtain additional training or credentials. Using a comparative individual fixed effects strategy and an administrative panel dataset of enrollment and employment in Virginia, we provide the first causal estimates of credential “stacking” among working adults. We find stacking increases employment by four percentage points and quarterly wages by $570 (seven percent). Returns are larger for individuals whose first credential is a short-term certificate and in Health and Business. Read full paper here.