ferences in health care costs among the states. Several other surveys, including the National Health Interview Survey and the State and Local Area Integrated Telephone Survey, have been used to estimate the number of children eligible for both SCHIP and Medicaid. Differences in methodology and in question format make for substantial variations in these estimates. In his presentation at the workshop, Thomas Selden concluded that each of the national surveys has positive and negative attributes and there is no single benchmark against which to compare results. The challenges include having to estimate eligibility from income data that do not map directly to state eligibility criteria, either in terms of the eligibility criteria for the state’s Medicaid program, the definition of insurance, the definition of countable income, or the length of the reference period for measuring income or insurance coverage; respondents’ difficulties in accurately responding to survey questions on income; differences in income thresholds across the states; nonresponse to the survey; and inadequate sample sizes to estimate the number of eligible children in all but the largest states, even when multiple years of survey data are combined.1

SCHIP is a state program with only general guidelines from the federal government, thus eligibility criteria vary from state to state. In particular, states were required to maintain Medicaid eligibility for all children who were eligible prior to June 1997 and to use SCHIP to provide insurance for children whose family income exceeds the level for Medicaid but whose income falls below the level set by the state as the income ceiling for SCHIP. The assessment of eligibility for SCHIP is complicated by the relationship between family income and the ceiling for Medicaid eligibility and SCHIP eligibility. The income band for eligibility for SCHIP is sufficiently narrow (in some states, for example, between 100 percent and 140 percent of the federal poverty level) that its boundaries are very difficult to identify from survey data, particularly in view of the difficulty in allocating survey responses to income questions and the difficulty that respondents have in supplying the information with the precision needed to accurately model eligibility. In most states, when family income changes only slightly, eligi


Beginning in the year 2001, the sample size of the March Supplement was increased to provide much more reliable estimates for the smaller states, in many cases more than doubling the sample size for the state. Since the state estimates for determining SCHIP allocations are based on a three-year average, the full effect of this change will not be realized until the year 2003.

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