The U.S. Census Bureau makes adjustments to the population controls in the Current Population Survey each January. That means the sample weights are revised so that estimates from the CPS agree with pre-specified national population totals by age, sex, race and Hispanic origin and with state level totals by age, sex and race. The annual adjustments to CPS weights are typically based on revised estimates of net international migration and updated vital statistics. Methodological changes also play a role. In the 2007 and 2008 population estimates, introduced into the CPS in January 2008 and January 2009, respectively, the Census Bureau made significant changes in the methodology used to measure international migration from 2000 onward. Another major revision was the introduction of the Census 2010 population base in January 2012.
The effect of the revision in January 2012, incorporating the new population base and other updated information, was to increase the estimate of the working-age population by 1,510,000, the labor force by 258,000 and the number of employed workers by 216,000 (“Adjustments to Household Survey Population Estimates in January 2012,” Bureau of Labor Statistics, February 2012). The effect of the annual revision in January 2013 was to increase the estimate of the working-age population by 138,000, the labor force by 136,000 and the number of employed workers by 127,000 (“Adjustments to Household Survey Population Estimates in January 2013,” Bureau of Labor Statistics, February 2013). Rates—for employment, labor force participation and unemployment—are either not affected or only slightly affected by the January CPS revisions.
The annual revisions of the CPS affect the comparability of labor force statistics over time. For example, the BLS-published estimate of the working-age population in December 2011 is 240,584,000, and the published estimate for January 2012 is 242,269,000 (nonseasonally adjusted). These estimates imply that the working-age population increased by 1,685,000 from December 2011 to January 2012. However, most of this increase—1,510,000 of the 1,685,000—is simply the result of revisions to the CPS in January 2012.
Labor market statistics published by the BLS are not revised historically to account for the effect of annual revisions to CPS weights or for the effect of introducing the Census 2010 population base. The estimates in this report are adjusted in two ways to account for the revisions of the CPS. First, the estimates for 2007 to 2008 are produced using reweighted data that incorporate the Vintage 2008 population estimates for the civilian non-institutional population (Vintage 2008 population controls were introduced into the CPS in January 2009). The new weights are derived using procedures that follow the weighting procedures of the U.S. Census Bureau (2006) to the extent possible with public-use data applied to Vintage 2008 population estimates—both published and unpublished data supplied by the U.S. Census Bureau to the Pew Research Center (see Passel and Cohn, 2010, for additional details).
Second, estimates for 2007 to 2012 are revised to account for the effects of CPS revisions from January 2010 to January 2013 using a BLS-published methodology (Di Natale, 2003). This methodology is used to produce revised estimates for the overall Hispanic and non-Hispanic populations, and for the white, black and Asian populations after making adjustments to remove Hispanics from these racial groups. The overall revisions to the Hispanic and non-Hispanic estimates are further allocated by nativity based on the distributions of the populations by nativity in any given quarter.
The main result of adjusting for the effects of the CPS revisions is to produce a smoother time series of the working-age population. This can be seen in the chart that shows the Hispanic working-age population from the first quarter of 2006 to the fourth quarter of 2013 before and after adjusting for CPS revisions. The revised series of CPS data leads to more accurate measures of changes over time in the working-age population, labor force and employment of various racial, ethnic and nativity groups.
