Association for Public Policy Analysis & Management

California continues to have a sizable population of uninsured residents even after implementation of coverage expansions under the Affordable Care Act. This is due, in part, to the large number of unauthorized immigrants without health insurance who are not eligible for federally subsidized coverage. Recent policy developments may provide opportunities for unauthorized immigrants in California to gain access to affordable coverage. Currently, the state provides full Medicaid benefits (Medi-Cal in California) to low-income, unauthorized immigrants who registered for the Deferred Action for Childhood Arrivals (DACA) program. Should the Deferred Action for Parental Accountability (DAPA) program be implemented, many low-income unauthorized adults in California could become eligible for Medi-Cal if the state continues covering those with deferred action status. In addition, state legislation has been proposed to expand health coverage to low-income unauthorized immigrants not eligible for deferred action. The bill (SB 4) would extend Medi-Cal to all income eligible residents regardless of immigration status and provide options to purchase coverage through a state-based insurance exchange (either the state’s existing exchange with a federal waiver or a separate exchange program) for those with higher incomes.

Anticipating the number of unauthorized immigrants who may be eligible for expanded coverage is not straightforward. Few estimates of this population are at a sub-state level or provide sufficient income detail. Low- and moderate-income unauthorized immigrants are not evenly distributed across the state. And given regional differences in health plans and provider capacity as well as insurance costs, information on the size and distribution of the state’s unauthorized population by income level is crucial to effectively plan for coverage expansions.

Our paper uses a novel approach to estimate the population of unauthorized immigrants within California’s counties and zip codes using administrative tax data. This method was used most recently in 2009 to calculate county-level estimates of unauthorized immigrants (Lee, Hill, and McConville 2012). We update county estimates to 2012 and extend the previous analysis to provide regional estimates of unauthorized immigrants by poverty level thresholds to approximate program eligibility for proposed coverage options. We develop our program-eligible estimates by first calculating average family size at the zipcode-level using tax return information on use of the federal child tax credit and tax filing status. We then calculate regression-based estimates of family size at various income categories within zip codes and use those to create shares of the unauthorized across regions that are likely program-eligible.

We report shares and counts of unauthorized immigrants falling into important poverty categories related to Medi-Cal eligibility and exchange coverage including: below 138%, between 138 –400%, and over 400% of the federal poverty level. Despite our focus on California – an important state given its share of all unauthorized immigrants in the country and state efforts to provide benefits to this group - the administrative tax data we rely on is available for all zipcodes across the country allowing this type of analysis to be extended to other states with large unauthorized populations.