The Bureau of Economic Analysis compiles statistics which is used for "decisions about interest rates and trade policy, taxes and spending, hiring and investing, and more." (Source: https://www.bea.gov/about/who-we-are)

For details on the methodology for GDP estimates, visit this website: https://www.bea.gov/resources/methodologies/gdp-gdi-revisions-source-data

The data is not based on individual demographic information but is a broad county-wide estimate.

The Bureau of Economic Analysis and U.S. Department of Commerce's data dissemination practices can be found here: https://www.bea.gov/about/policies-and-information/data-dissemination