Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
The paper tests whether the impact of prenatal care on birthweight is contaminated by selection bias, and if so, whether adverse or favorable selection dominates. A two-stage selectivity correction model with an ordered criterion function is applied to race- and ethnic-specific data from 1984 New York City birth certificates. We find that ordinary least squares underestimates the effects of prenatal care on birthweight by at least 80 percent for whites and Hispanics. The results point to adverse selection in the demand for prenatal care.