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The Harvey L. Neiman Health Policy Institute® studies the value and role of radiology in evolving health care delivery and payment systems, including quality based approaches to care and the impact of medical imaging on overall health care costs. Neiman Institute research provides a foundation for evidence-based imaging policy to improve patient care and bolster efficient, effective use of health care resources.

Medicare Beneficiary Enrollment Numbers: A Research Tool

The Harvey L. Neiman Health Policy Institute was established to study the policy implications of evolving healthcare delivery and payment systems on radiologists and radiology more broadly.

One aspect of carrying out this mission is to conduct research analyzing how the utilization of procedures has changed over time. Most such work has been done on Medicare fee for service beneficiaries. However, the number of procedures can change from one year to the next based solely on changes in the number of Medicare enrollees.

In order to account for this change, HPI’s research routinely reports utilization per 1,000 or 10,000 Medicare fee-for-service beneficiaries. To do this, however, researchers not only need to know how many services were rendered but also the number of covered beneficiaries at that time.

Increasingly, more Medicare beneficiaries are covered under Medicare Advantage Plans managed through private payers. Information about these – and other people not covered by government-provided insurers – is much less accessible and more difficult to acquire. For these reasons, the HPI and other health policy research groups have tended to focus much of their work on the Medicare fee-for-service population.

The way that the Centers for Medicare & Medicaid Services (CMS) calculates the number of enrollees has changed over time, making it difficult for researchers to transparently and consistently calculate utilization. A prior HPI blog has focused on this topic: How Many Medicare Enrollees? CMS Methodological Changes and Implications for Research.

In an effort to facilitate imaging-focused health policy research by others, the HPI is now making our estimates of the number of Medicare fee-for-service beneficiaries publicly available. For enrollment data up through 2012, we have relied on prior CMS enrollment files from 1966 through 2012, previously available here: 2013 Medicare and Medicaid Statistical Supplement.

Unfortunately, CMS is no longer maintaining these files. For enrollment after 2012, we are relying on annual files CMS has made available here: CMS Program Statistics and specifically using Part B Total enrollment numbers listed on each year’s AB9 Table.


Here are the last ten years of data. To obtain all years of available data, please see the EXCEL and other data type links below. We anticipate updating these files annually.



YEAR Medicare Part B Enrollment
2018 33,366,109
2017 33,562,359
2016 33,715,448
2015 33,286,965
2014 33,189,779
2013 33,147,099
2012 32,938,541
2011 32,583,807
2010 32,236,473
2009 31,859,475



Full Medicare Beneficiary Enrollment Numbers Version 1.0 (Original 3/18/2020)

Medicare Beneficiary Number EXCEL 1.0

Medicare Beneficiary Numbers STATA 1.0

Medicare Beneficiary Numbers SAS 1.0

Medicare Beneficiary Numbers SPSS 1.0



Please cite this data as “Harvey L. Neiman Health Policy Institute Medicare Beneficiary Enrollment Tool. Accessed: mm/dd/yyyy”


HPI Blog: How Many Medicare Enrollees? CMS Methodological Changes and Implications for Research.