Calculating Sub-county Area Labor Force Data for Historical Time Periods

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Labor force data for sub-county areas are available for the most current month and annual averages only. The following instructions will assist users in calculating data for other time periods.

Monthly labor force data for sub-county areas are calculated by using the share of county-level employment and unemployment in the area at the time of the most current five-year American Community Survey (ACS) estimates, which are updated annually.  The sub-area’s employment and unemployment estimates are then added to determine the total labor force and unemployment rate.

This method assumes that the rates of change in employment and unemployment are exactly the same in each sub-county area as at the county level (the same process is used for unemployment). If this assumption is not true for a specific sub-county area, then the estimates for that area may not be representative of the current economic conditions. Since this assumption is untested, caution should be employed when using these data.

Find the Ratios

Locate the sub-county data file for the county in which the sub-county area is located. You may want to view the file to verify that the area you need is available. The data in this file should look like this:


  • Labor Employ- Unemployment Emp Unemp Area Name Force ment Number Rate Ratio Ratio Column (1) (2) (3) (4) (5) (6) Amador County 18,900 17,400 1,500 7.7% 1.000000 1.000000 Amador City - city 200 200 0 4.2% 0.009184 0.004839 Ione - city 1,900 1,800 100 5.7% 0.100661 0.072581 Jackson - city 2,600 2,400 200 6.8% 0.138134 0.119355 Plymouth - city 500 500 0 2.5% 0.031227 0.009677 Sutter Creek - city 1,500 1,400 100 9.3% 0.081337 0.100000

At this point, you may want to write down the employment and unemployment ratios in columns (5) and (6), or save the entire document for future reference. These ratios will remain constant until the next decennial federal census.

Find County Data

Now find the county labor force file containing employment and unemployment data for the time period of interest to you. The best files to use are the historical data available on the Labor Force page. These files are available for individual counties. Here is a sample of this file:

  • Civilian Labor Force, Employment, and Unemployment Amador County March 2007 Benchmark; Data are not seasonally adjusted Notes: 1) The unemployment rate is calculated using unrounded data. 2) Labor force data for all geographic areas for 1990 to 2007 now reflect the March 2007
    annual revision (or benchmark) and Census 2000 population controls at the state level. Source: Employment Development Department, Labor Market Information Division, 916-262-2162, 2008 Labor Force Employment Unemployment U.E. Rate January 18,240 16,870 1,370 7.5% February 18,220 16,920 1,300 7.2% March 18,320 16,940 1,380 7.5%

You can also find the county data in "Labor Force Data for Counties Report". These reports list labor force data for all counties by month.

Calculate City Data

To calculate sub-county area labor force data, multiply the county employment and unemployment figures by the respective employment and unemployment ratios for the desired sub-area. The results represent the employment and unemployment for the sub-area for that time period.

Civilian labor force is the sum of the area’s employment and unemployment. The unemployment rate is calculated by dividing unemployment by the civilian labor force then multiply by 100.

Using the data above, calculate the unemployment rate for the City of Ione in Amador County for January 2008.

  • Ratios for City of Ione (2000 Census):
    • Employment: 0.100661
    • Unemployment: 0.072581
    Data for Amador County (January 2008):
    • Employment: 16,870
    • Unemployment: 1,370
    Calculations for City of Ione for January 2008:
    • Employment: 0.100661 * 16,870 = 1,698
    • Unemployment: 0.072581 * 1,370 = 99
    • Civilian Labor Force: 1,698 + 99 = 1,797
    • Unemployment Rate: (99 / 1797) x 100 = 5.5%