Using Discontinuous Eligibility Rules to Identify the Effects of the Federal Medicaid Expansions on Low Income Children

This paper exploits the discrete nature of the eligibility criteria for two major federal expansions of Medicaid to measure the effects on Medicaid coverage, overall health insurance coverage, and the probability of visiting a doctor. The '100 percent' expansion, effective in 1991, extended Medicaid eligibility to children born after September 30, 1983 in families below the poverty line. We estimate that this law led to about a 10 percentage point rise in Medicaid coverage for children born just after the cutoff date, and a similar or slightly smaller rise in overall health insurance. It also increased the fraction of children in the newly eligible group with a doctor visit in the previous year. The '133 percent' expansion, effective in 1990, extended Medicaid to children under 6 in families with incomes below 133 percent of the poverty line. This law had relatively small effects on Medicaid coverage for children near the eligibility limits, and little or no effect on health insurance coverage.

Using Discontinuous Eligibility Rules to Identify the Effects of the Federal Medicaid Expansions on Low Income Children

Despite intensive scrutiny, the effects of Medicaid expansions on the health insurance status of low-income children remain controversial. We re-examine the effects of the two largest federally-mandated expansions which offered Medicaid coverage to low-income children in specific age ranges and birth cohorts. We use a regression discontinuity approach, comparing Medicaid enrollment, private insurance coverage, and overall insurance coverage on either side of the age limits of the laws. We conclude that the modest impacts of the expansions on health insurance coverage arose because of very low takeup rates of the newly available coverage, rather than from crowd-out of private insurance coverage.

The Measurement of Medicaid Coverage in the SIPP : Evidence from a Comparison of Matched Records

This paper studies the accuracy of reported Medicaid coverage in the Survey of Income and Program Participation (SIPP) using a unique data set formed by matching SIPP survey responses to administrative records from the State of California. Overall, we estimate that the SIPP underestimates Medicaid coverage in the California population by about 10 percent. The probability that a SIPP respondent who is covered by Medicaid in a given month correctly reports their coverage is around 85 percent. The corresponding probability for low-income children is higher – around 90 percent. Under-reporting by those who are actually in the Medicaid system is partially offset by over-reporting of coverage by people who are not. Some of these false positive responses are attributable to errors and missing data in the administrative system, rather than to problems in the SIPP. Taking account of these errors, the estimated false positive rate for the population as a whole is about 1.5 percent, and 4-5 percent for poor children.

The Measurement of Medicaid Coverage in the SIPP: Evidence from California, 1990-1996

This paper studies the accuracy of reported Medicaid coverage in the Survey of Income and Program Participation (SIPP) using a unique data set formed by matching SIPP survey responses to administrative records from the State of California. Overall, we estimate that the SIPP underestimates Medicaid coverage in the California population by about 10 percent. Among SIPP respondents who can be matched to administrative records, we estimate that the probability someone reports Medicaid coverage in a month when they are actually covered is around 85 percent. The corresponding probability for low-income children is even higher - at least 90 percent. These estimates suggest that the SIPP provides reasonably accurate coverage reports for those who are actually in the Medicaid system. On the other hand, our estimate of the false positive rate (the rate of reported coverage for those who are not covered in the administrative records) is relatively high: 2.5 percent for the sample as a whole, and up to 20 percent for poor children. Some of this is due to errors in the recording of Social Security numbers in the administrative system, rather than to problems in the SIPP.

Fast Rotation and Trailing Fragments of the Active Asteroid P/2012 F5 (Gibbs)

While having a comet-like appearance, P/2012 F5 (Gibbs) has an orbit native to the Main Asteroid Belt, and physically is a km-sized asteroid which recently (mid 2011) experienced an impulsive mass ejection event. Here we report new observations of this object obtained with the Keck II telescope on UT 2014 August 26. The data show previously undetected 200-m scale fragments of the main nucleus, and reveal a rapid nucleus spin with a rotation period of 3.24 $\pm$ 0.01 hr. The existence of large fragments and the fast nucleus spin are both consistent with rotational instability and partial disruption of the object. To date, many fast rotators have been identified among the minor bodies, which, however, do not eject detectable fragments at the present-day epoch, and also fragmentation events have been observed, but with no rotation period measured. P/2012 F5 is unique in that for the first time we detected fragments and quantified the rotation rate of one and the same object. The rapid spin rate of P/2012 F5 is very close to the spin rates of two other active asteroids in the Main Belt, 133P/Elst-Pizarro and (62412), confirming the existence of a population of fast rotators among these objects. But while P/2012 F5 shows impulsive ejection of dust and fragments, the mass loss from 133P is prolonged and recurrent. We believe that these two types of activity observed in the rapidly rotating active asteroids have a common origin in the rotational instability of the nucleus.Comment: To appear in the 2015 March 20 issue of ApJ Letter