U.S. Bureau of Labor Statistics 

Current Population Survey (CPS) 

Technical Documentation

February 2019

Labor Force and Employment Research Series

Smoothed for Population Control Adjustments 

Background

Population controls are independent estimates of population used to weight the Current 

Population Survey (CPS) sample results to reflect the civilian noninstitutional population age 16 

and older. 

The U.S. Census Bureau develops the population controls for the CPS. The controls are based on 

decennial census population counts, supplemented with birth and death data and estimates of net 

international migration. Each year, the Census Bureau adjusts the controls to include the latest 

information about population change and to incorporate any improvements in the estimation 

methodology.

The Bureau of Labor Statistics (BLS) introduces the annual population control adjustments into 

the CPS estimates with data for January. BLS typically does not revise the historical CPS data 

series to reflect the updated controls because of the extensive effort needed to regenerate and 

verify the many time series produced from the CPS, and because the revisions tend to be 

negligible for most series.

Time series comparability issues and the introduction of smoothed series

Substantial adjustments to the population controls in some years resulted in December–January 

level shifts that created data comparability problems, particularly the national labor force and 

employment levels. In December 2003, as a convenience to data users, BLS outlined a method to 

smooth level shifts in these two series. The method distributes the amount of the level shift 

incrementally back to January of the relevant decennial census base year, rather than 

incorporating the entire change in January of the year in which it was implemented. (For more 

information, see Marisa L. DiNatale, Creating Comparability in CPS Employment Series.) The 

smoothed series always ends with the December prior to the latest January population control 

adjustment, and is meant to be used with current-year data from the official series.

Notice to Smoothed Series Data Users

BLS will no longer update the smoothed labor force and employment research series.

These series, which run from January 1990–December 2017, were last updated in 

February 2018.

They will remain available online for interested data users, but no further extensions or 

revisions to the series are planned.
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In the initial application of the smoothing method, BLS distributed the January 2000 and January 

2003 level shifts that resulted from the introduction of Census 2000-based population controls 

over the relevant historical time periods for each. The January 2000 level shift, which 

represented the difference between the 1990 census-based estimates and those based to Census 

2000, was smoothed from January 1990 through December 1999. The January 2003 level shift, 

which represented estimated population growth since Census 2000, was smoothed from January 

2000 through December 2002.

BLS provided updated versions of these smoothed labor force and employment research series in 

subsequent years, following significant adjustments to the Census 2000 population base. Each 

time, the research series were smoothed from January 2000 forward. Data for 1990–1999 were 

not further revised.

With release of data for January 2012, BLS incorporated the first population controls based on 

Census 2010; following previous practice, this adjustment effect was smoothed from January 

2000 through December 2011. Subsequent updates to the research series smoothed out the 

effects of intercensal adjustments to the Census 2010 population base made from January 2013–

January 2018. Those adjustments represented estimated change in the population since Census 

2010 and were therefore smoothed back to January 2010. Data for earlier years were not further 

revised. 

The smoothings may be summarized as follows:

 Data from January 1990– December 1999 were smoothed for the Census 2000 population 

control adjustment.

 Data from January 2000–December 2010 were smoothed for intercensal adjustments to 

the Census 2000 population base implemented in January 2003–2011.

 Data from January 2000–December 2011 were smoothed for the Census 2010 population 

control adjustment introduced in January 2012.

 Data from January 2010–December 2017 were smoothed for intercensal adjustments to 

the Census 2010 population base implemented in January of 2013–2018.

In fall 2018, BLS announced the discontinuation of the smoothed labor force and employment 

research series. The last versions of the series, which run from January 1990–December 2017, 

will remain available online for interested data users, but no further extensions or revisions to the 

series are planned.

 Smoothed labor force research series: www.bls.gov/cps/smoothed_lf.xlsx 

 Smoothed employment research series: www.bls.gov/cps/smoothed_emp.xlsx 

Data users should note that the smoothed research series will not match the official CPS 

estimates in BLS publications and on the BLS website. In addition, these research data would 

differ from those calculated using other smoothing methods.