Data Quality for Puerto Rico Dual Eligibles
Published on Sep 21, 2026 by Rebecca Vick
It came to my attention that the MBSF indicates an unbelievably low dual eligibility rate for Puerto Rico.
Identifying Medicare Advantage and Fee-for-Service Beneficiaries in the Master Beneficiary Summary File
Background
Medicare beneficiaries may enroll in a private managed care plan (Medicare Advantage (MA)) or in Fee-for-Service (FFS) Medicare (Original Medicare). The Master Beneficiary Summary File (MBSF) includes all beneficiaries enrolled in Medicare for at least one day of the year and contains variables that distinguish MA from FFS enrollment(1). Medicare Research Identifiable Files (RIFs) that contain utilization data include only subsets of beneficiaries depending upon how they are enrolled.