This study focuses on network effects' in the utilization of publicly funded prenatal care using Vital Statistics data from California for 1989 to 2000. Networks are defined using 5-digit zipcodes and a woman's racial or ethnic group. Like others, we find evidence that the use of public programs is highly correlated within groups defined using race/ethnicity and neighborhoods. These correlations persist even when we control for many unobserved characteristics by including zipcode-year fixed effects, and when we focus on the interaction between own group behavior and measures of the potential for contacts with other members of the group ( contact availability'). However, the richness of our data allows us to go further and to conduct several tests of one hypothesis about networks: That the estimated effects represent information sharing within groups. The results cast doubt on the idea that the observed correlations can be interpreted as evidence of information sharing, and point instead to differences in the behavior of the institutions serving different groups of low-income women as the primary explanation for group-level differences in the take-up of this important public program.

During the 1990s many states extended Medicaid eligibility to low-income parents who were not receiving welfare. We evaluate the effects of those expansions on health insurance coverage. To account for unobservable differences between expansion states and non-expansion states that may be correlated with both policy decisions and insurance coverage, we employ a within-state difference-in-difference technique that makes use of data only from expansion states. We find that the parental eligibility expansions increased Medicaid coverage of mothers with only small effects on private coverage. The expansions also increased the coverage of children, presumably by raising the benefit to the family of applying for coverage. We find substantial racial and ethnic differences in the effects of the expansions. As a result, the expansions help reduce racial and ethnic gaps in insurance coverage, particularly for adults.