GCP was originally an experimental dataset released by the BEA for the first time in the fall of 2018. As of December 12, 2019, it was released as an official product. Shortly after that, Emsi investigated the data with an eye toward incorporating it into our calculation of Gross Regional Product at the county and ZIP levels.
Emsi has elected not to use the BEA’s GCP product, mostly because of the BEA’s lack of component detail. Both BEA and Emsi use the income approach when calculating GDP (or GRP or GCP). The income approach sums four components–earnings, taxes, and profits, less subsidies–to arrive at a final figure for GCP. The BEA produces earnings and the part of profits that come from proprietors at the county level as part of their Personal Income dataset, but the remainder of profits, as well as the whole of taxes and subsidies, are estimated as one remainder component of GCP by proportioning down to the county from known state GDP figures. Since Emsi publishes each component of GCP individually, switching to BEA’s GCP values would necessitate Emsi’s publishing GCP as one comprehensive measure and eliminate our ability to publish the individual components.
Additionally, there is some question on the BEA’s use of potentially unhelpful source data to calculate GCP for some industries, specifically the use of FDIC data to calculate the remainder component for the Banking industry. This use of FDIC data as source data has caused one of Emsi’s clients to call into question the validity of BEA GDP estimates for their area.
The BEA hasn’t yet released detailed methodology describing how they calculate GCP. Once this document is released, Emsi will evaluate the BEA’s methodology and make a final decision on whether to attempt to incorporate this dataset into Emsi GRP data.
See this article to read Emsi’s methodology for calculating GRP.