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Master Beneficiary Summary File (MBSF) - Base Segment Files

Medicare

Description

Our Master Beneficiary Summary File (MBSF) - Base Segment (A/B/C/D) files have the following data about individuals enrolled in Medicare between 1999 and 2018:

  • beneficiary demographics;
  • eligibility status; and
  • plan enrollment.

For 1991 - 1998 data, refer to the Denominator (DN) Files.

Variables Summary

The table below lists variable categories for and some key variables in MBSF - Base Segment data. For a comprehensive list of variables, review the MBSF - Base Segment data dictionary.

Demographics

Age, Beneficiary Identification Number, Date of Birth, Date of Death, Gender, Race, Residence County Code, Residence State, Residence Zip Code

Eligibility & Enrollment

Dual Eligibility Status, Monthly Enrollment Counts (A/B/C/D), Part C Plan and Enrollment Information, Part D Low-Income Cost Sharing, Part D Plan and Enrollment Information, Reasons for Entitlement, State Buy-In Indicators

Years Available

1999 - 2018

Data Dictionary Link

Visit the Data Documentation Page

NIA Surveys Offering MBSF

CE, HRS, LLFS, NSHAP, PT, PSAD, PSID, RADC, UFOVT, WLS

NIA Surveys Not Offering MBSF

BLSA, HABC, NHAS, NHATS, NLTCS, UAS

Additional Resources

Denominator (DN) Files