NHSC Administrative File
The NHSC administrative file provided to us by HRSA represents a panel of 22,703 participants who entered the NHSC programs over the period 2000-2013. The NHSC administrative file contains information on where each participant was located each year during the participant’s program (down to the zip code level). Participants are tracked annually from their entry year until 2013, but only while they are in the program. Of the total number of providers, 10,123 are physicians, 6,850 are nurse practitioners (NP) or physician assistants (PA) and the remaining 5,730 individuals represent other providers, such as dental or behavioral health providers. This database contains information on participant demographics and award/service characteristics, including: age, gender, race/ethnicity, award year, entry year, type of award, length of initial service obligation, funds received, practice type, provider type, location, and separation year. Table II.1 provides a breakdown of the number of NHSC enrollees by entry year, provider type, gender, program type, average age on entry, and race/ethnicity.
Table II. 1: Select Socio-Demographic Characteristics of NHSC Enrollees by Entry Year
The number of new NHSC participants has increased substantially over the last few years, with most of this increase reflected in an expansion in the number of women, non-physicians and White providers. In Appendix Table B.1 we present the distribution of the NHSC workforce by provider discipline.
In Table II.2 we present the number of records on NHSC providers by entry cohort.
Table II. 2: Number of Records on NHSC Providers by Entry Cohort
The main disadvantage of the NHSC administrative data file is that it does not include information on where participants were located after program completion. Also, it does not contain the participant’s National Provider Identification (NPI) number, or other unique identifiers which would enable us to track their location after program completion. We therefore rely on additional data sources to identify the participants’ NPI and then subsequently determine where they were located after program completion. These four data sources, which are also used to identify non-participant providers, include:
AMA Physician Master Files of various years since 2000;
Medicare Providers File developed from Medicare claims data over the period 2005-2011; and
Optum Corporation’s Provider 360 File, a proprietary file containing comprehensive information on most medical providers in the United States.
Finally, we employ data from HRSA with information on HPSA designations, types, disciplines, sites and scores. We use the most recent file of these data, which was compiled in December 31, 2013.
Below we discuss these files in turn and highlight their advantages and limitations for the current project.
AMA Physician Master Files
The AMA Master file was begun in 1986 and has been tracking physicians since then. Multiple years of AMA data were extracted to obtain information about provider location over multiple years. Each year of the AMA data file contains current information on the physicians’ locations and practices, along with information on their training. The AMA is the single most comprehensive data source on physicians practicing in the US. In theory, linking NHSC administrative data with the AMA data, it is possible to track the practice location and retention information of NHSC enrollees over the years. Each observation includes location data (such as zip code), medical school, specialty, graduation year, birth date, race, and gender. We make use of complete AMA Physician Master Files for the following years: 2000, 2007, 2008, 2010-2012, and partial files (containing only data on primary care providers) for 2003 and 2005. The number of records increased steadily from about 1.0 million physicians in 2000 to about 1.3 million in the 2011 file. However, the main limitations of these files are that they include only physicians and that the providers’ location is updated infrequently, at intervals that are often longer than one year.
Provider360 (P360) is a comprehensive provider database developed and maintained by OptumInsight, the Lewin Group’s parent company. Optum first developed Provider360 in the early 2000s and since then has updated it on a monthly basis. Optum links numerous private and public databases to create P360, and it gathers information about each provider’s demographics, education and training, NPI and DEA numbers, and location. Importantly, Provider360 contains both physician and non-physician providers, including PAs, NPs, and mental health and dental care clinicians.
This dataset covers virtually all currently active providers and includes most of the socio-demographic variables that we observe in the NHSC data, like provider demographics or provider type, as well as additional useful variables, like the provider’s NPI, medical education and practice affiliation. The large number of common variables appearing both in the NHSC files and P360, like name, birthdate, gender and others, allows for a link between the two datasets with a good match rate.
The main limitation of P360 is that it was not designed to provide panel information about providers, so we can tell where providers are located now but not each year in the past. However, even without historical P360 data retention patterns of NHSC providers can be constructed by comparing their locations upon NHSC program completion with their current locations in P360. For instance, we can look at the cohort of students finishing their medical training in, say, 2006 and determine how many of them are still serving in HPSAs as of the current year. We return to this point in the next section of this chapter. Other useful variables available in P360 include the provider’s degree, specialty, medical school attended, residency institution, license, DEA number, hospital affiliation, practice type, practice NPI, and sanctions against the provider.
Medicare Providers File
In order to track participants and non-participants over time, we constructed a provider level dataset using the Medicare claims of providers who billed Medicare between 2005 and 2011. In this dataset the unit of observation is the provider-year, meaning that each Medicare provider is observed annually along with his or her geographical location at the zip code level. The provider’s location in a given year is based on the most frequent zip code associated with that provider’s claims during that year. The dataset includes the provider’s NPI, which allows us to identify NHSC participants and track their location in the years after their service completion.
The Medicare provider file contains 5,757,405 observations on 1,099,836 unique providers. The breakdown of unique providers by type is: 626,836 physicians, 123,223 NP/PA’s, 54,168 DO’s and 295,615 other providers. Table II.3 shows the number of providers by type in each year.
Table II. 3: Number of Providers by Type in Each Year (Medicare Provider Data)
As in the case of another provider data, available to the Lewin team known as the de-Identified Normative Health Information (dNHI) data, Medicare providers also appear to be well distributed across all states during the period between 2005 and 2011 (Appendix Table B.2).