To explore these topics, we used a customized data set constructed at the provider level. This data set includes all the claims submitted by the entire universe of Medicare providers in each year from 2005 to 2011. The content of this customized data set is similar to the Limited Data Set (LDS) version of the Medicare Carrier File (which is also known as the Physician/Supplier Part B Claims) available from CMS Research Data Assistance Center (RESDAC). Subsequently, in the discussion that follows we will refer to the customized claims level data set for all Medicare providers as the Provider Carrier File (PCF). Most of the claims in our PCF are from non-institutional providers, such as physicians, physician assistants, clinical social workers, and nurse practitioners. Key variables in this file include:
Procedure codes (HCPCS) corresponding to each claim
Provider total allowable charges associated with all claims
Provider specialty, place of service, and geographic location (such as zip code)
We constructed a provider level pooled data set (PPD) from the claims level data in the PCF over the period 2005-2011. This pooled data set includes information such as provider specialty, volume of primary care services (based on HCPCS codes), volume of PCIP eligible services, distribution of providers by volume of services, their annual Medicare allowed charges, their geographic location, and other related information, over a longer time horizon. In addition, the original PCF included a National Provider Identifier (NPI) for each provider. Subsequently, each provider was linked by NPI to Provider360 data (available from Lewin Group’s parent company Optum Inc.) and the AMA Physician Master File to add provider characteristics such as provider demographics (e.g., age, gender), provider designation, medical school, practice group information, specialty and practice location. We also added geographic location specific characteristics by linking the provider level data with the Area Resource File (ARF) based on the practice location information of providers. The ARF data are maintained by the Health Resources and Services Administration (HRSA). The main advantage of this pooled data set is the ability to track providers over time and capture changes in their volume of services in response to Medicare payment incentives using a pre-and-post analysis design.