Relevant indicators:

• Job and GDP growth
• Economic gains: Racial equity in income (GDP gains breakdown only)

Data presented on GDP is from the U.S. Bureau of Economic Analysis (BEA). However, due to changes in the estimation procedure used for the national (and state-level) data in 1997, a lack of metropolitan area estimates prior to 2001, and no available county-level estimates for any year, a variety of adjustments and estimates were made to produce a consistent series at the national, state, metropolitan areas, and county levels from 1969 forward. While the county data are not currently included in the Atlas, they were used to build a consistent set of metro-area estimates over time.

Adjustments at the state and national levels

It was necessary to generate an adjusted series of state GDP because of a change in BEA’s estimation procedure from a Standard Industrial Classification (SIC) basis to a North American Industry Classification System (NAICS) basis in 1997. Data prior to 1997 were adjusted to avoid any erratic shifts in GDP that year. While the change to NAICS basis occurred in 1997, BEA also provides estimates under a SIC basis in that year. Our adjustment involved calculating the 1997 ratio of NAICS-based GDP to SIC-based GDP for each state, and multiplying it by SIC-based GDP in all years prior to 1997 to obtain our adjusted series of state-level GDP.

The adjusted series of state-level GDP was then used to derive national GDP and to estimate GDP at the county and metro-area levels as necessary (as described below). To maintain consistency with the state data, GDP for the nation was calculated as the sum of GDP by state, and may differ from national GDP reported elsewhere for the following reasons: GDP by state excludes federal expenditures on personnel stationed abroad and on military structures and military equipment located abroad (except office equipment), while these are typically included in national GDP; GDP by state and national GDP have different revision schedules.

County and metropolitan area estimates

To generate county-level estimates for all years and metropolitan-area estimates prior to 2001, a more complicated estimation procedure was followed. First, an initial set of county estimates for each year was generated by taking our adjusted series of state-level GDP and allocating it to the counties in each state in proportion to the total earnings of employees working those counties—a BEA variable that is available for all counties and years. Next, the initial county estimates were aggregated to metropolitan area level, and were compared with BEA’s official metropolitan area estimates for 2001 and later (which follow the same December 2003 metro-area definitions used in the Atlas). They were found to be very close, with a correlation coefficient very close to one (0.9997). Despite the near-perfect correlation, we still used the official BEA metro-area data in our final data series for 2001 and later. However, to avoid any erratic shifts in gross product during the years leading up to 2001, we made the same sort of adjustment to our estimates of gross product at the metro-area level that was made to the state and national data pre-1997—we figured the 2001 ratio of the official BEA estimate to our initial estimate, and multiplied it by our initial estimates for 2000 and earlier to get our final estimate of gross product at the metro-area level.

We then generated a second iteration of county-level estimates—only for counties included in metro areas—by taking the final metro-area–level estimates and allocating gross product to the counties in each metro area in proportion to the total earnings of employees working in those counties. Next, we calculated the difference between our final estimate of gross product for each state and the sum of our second-iteration county-level gross product estimates for counties contained within metro areas in the state. This difference, total nonmetropolitan gross product by state, was then allocated to the nonmetropolitan counties in each state, once again using the total earnings of employees working in each county as the basis for allocation. Finally, because some metro areas cross state boundaries, one last set of adjustments was made to all county-level estimates to ensure that the sum of gross product across the counties contained in each metropolitan area agreed with our final estimate of gross product by metropolitan area, and that the sum of gross product across the counties contained in a state agreed with our final estimate of gross product by state. This was done using an IPF procedure.