Methodology: About the Medicaid and CHIP Enrollment Report

All states (including the District of Columbia) are required to provide data to The Centers for Medicare & Medicaid Services (CMS) on a range of indicators related to key application, eligibility, and enrollment processes within the state Medicaid and Children’s Health Insurance Programs (CHIP). These data reflect enrollment activity for all populations receiving comprehensive Medicaid and CHIP benefits in all states, as well as state program performance. CMS publically releases these eligibility and enrollment data collected from states in monthly reports.

Preliminary and Updated Data

In Medicaid, individuals are potentially eligible for retroactive coverage for incurred health care costs dating back to 90 days prior to the date of application. Also, states may not process all applications within a given month that they have been received. To capture the most complete enrollment data possible, states report two types of data: preliminary and updated. States report preliminary data approximately one week after the close of the reporting period, and it generally does not include retroactive enrollment or Medicaid and CHIP eligible individuals who applied during the reporting period but whose applications were not fully processed before the end of the month. Conversely, updated data is reported one month after the close of the reporting period and includes data for these two groups. CMS releases updated data for the previous month with each current monthly report.

Because updated data contains retroactive enrollments and preliminary data does not, the two types of data are not comparable. Only data of the same type should be compared across months (e.g., preliminary compared to preliminary). Please note, however, many states continue to adjust their reporting methodologies to better align with CMS’s data specifications. The data context notes below and the state-specific notes in the report tables highlight these changes. In some cases, methodological changes prevent data of the same type from being perfectly comparable.

Baseline Enrollment Data

The monthly reports use the three-month period prior to the start of the initial Marketplace open enrollment (July through September 2013) as the baseline period. States’ baseline enrollment figures represent an average of their Medicaid and CHIP enrollment from July through September 2013. Baseline enrollment figures include updated data, therefore comparing preliminary monthly data to the baseline slightly understates enrollment growth.

Prior Months’ Preliminary and Updated Reports

States update their preliminary data one month after the close of the reporting period to include any enrollment and eligibility activity that was not captured in their preliminary report. Updated data and prior months’ reports is available on the Monthly Medicaid and CHIP Application, Eligibility Determination, and Enrollment Reports and Updated Data page.