Technical information: Revisions to CES data for late sample reports, annual benchmarking, and other factors
Background
The Current Employment Statistics (CES) program (also known as the payroll survey or the establishment survey) is designed to measure trends in employment, hours, and earnings by industry. Each month BLS surveys approximately 141,000 businesses and government agencies representing approximately 486,000 worksites throughout the United States. The monthly Employment Situation news release provides national CES data on employment, hours, and earnings, as well as labor force and unemployment estimates from the Current Population Survey (CPS), also known as the household survey.
The Employment Situation is typically released on the first Friday of the month following the reference month. For example, the February 3, 2012 Employment Situation published CES first preliminary employment estimates for January 2012. CES estimates represent information reported by survey respondents for their pay periods that include the 12th of the month.
Not all sampled firms are able to report their data in time to be used in the first preliminary estimates. Therefore, BLS continues to collect sample responses after the release of first preliminary estimates for incorporation into second preliminary and final sample-based estimates. Second preliminary estimates for a reference month are published the month following the initial release, and final sample-based estimates are published two months after the initial release.
Sample-based estimates remain final until employment levels are reset to universe employment counts, or benchmarks, for March of each year; the benchmarks are primarily derived from Unemployment Insurance (UI) tax records. The annual benchmarking process results in revised data back to the last annual benchmark for not seasonally adjusted series and back five years for seasonally adjusted series.
CES data are principal economic indicators and serve as input to many other economic series. Each time the CES employment estimates are revised, additional information that was not previously available is incorporated into the estimates. Below are discussions of how CES data revise:
Monthly, to include late sample reports;
Annually, due to benchmarking; and
Irregularly, to avoid discontinuities while incorporating methodological changes.
Monthly Revisions to Include Late Sample Reports
CES data users typically are most concerned with revisions to over-the-month changes. This section profiles these monthly revisions of CES seasonally adjusted over-the-month changes and the sample collection rates that underlie the revisions.
Revisions to CES over-the-month changes are calculated by comparing each month's second preliminary over-the-month change to the first preliminary over-the-month change, the final sample-based over-the month change with the second preliminary over-the-month change, and the final sample-based over-the-month change to the first preliminary over-the-month change.
See
www.bls.gov/web/empsit/cesnaicsrev.htm for a table of revisions to seasonally adjusted Total nonfarm over-the-month changes from January 1979 forward. The monthly employment change figures shown in the table do not reflect subsequent changes due to the introduction of benchmark revisions, seasonal adjustment, or other updates.
Mean revisions and mean absolute revisions for each calendar year are included in the table. Mean absolute revisions indicate the overall magnitude of change to the estimates, while the mean revisions are a measure of whether there is a bias in direction of the revisions. The closer the mean revision is to zero, the less indication that revisions are predominantly either upward or downward. For example, if in a given year there were six upward revisions of 50,000 and six downward revisions of 50,000, the mean revision would be zero; however, the mean absolute revision would be 50,000.
BLS begins collecting sample reports for a reference month as soon as the reference period, the establishment's pay period that includes the 12th of the month, is complete. Collection time available for first preliminary estimates ranges from 9 to 15 days, depending on the scheduled date for the Employment Situation news release. The Employment Situation is scheduled for the third Friday following the week including the 12th of the prior month, with an exception for January. (For January, the news release is delayed a week if the third Friday following the week of the 12th occurs on January 1, 2, or 3.)
Given this short collection cycle for the first preliminary estimates, many establishments are not able to provide their payroll information in time to be included in these estimates. Therefore, CES sample responses for the reference month continue to be collected for two more months and are incorporated into the second preliminary and final sample-based estimates published in subsequent months. Additional sample receipts are the primary source of the monthly CES employment revisions.
Prior to 1991, most of the CES sample was collected by mail in a decentralized environment by each State Workforce Agency. BLS has gradually centralized collection and adopted automated sample collection methods with the result that collection rates have gradually risen over time. BLS uses a variety of collection techniques, tailored to individual firm preferences to encourage participation in this voluntary survey. Computer Assisted Telephone Interviewing (CATI) is used for initial enrollment and collection of sample. Sample units are often transferred later to an automated method of self-reporting, such as through Fax, Internet, or Touchtone Data Entry (TDE). Many large, multi-establishment firms report through Electronic Data Interchange (EDI); the firms provide electronic files to BLS that include all of their worksites. A small percentage of sample units still report via mail.
Collection rates are defined as the percent of reports received for a monthly estimate compared to the total number of actively-reporting sample units on the sample registry.
CES collection rates back to 1981 can be found on
www.bls.gov/web/empsit/cesregrec.htm.
Much of the month-to-month variation in the first preliminary collection rates is a function of the number of collection days in the individual months. The overall upward trend over time is attributable to replacing decentralized mail collection with automated techniques.
Benchmark Revisions
Annual CES benchmark revisions are published along with January first preliminary estimates in February of each year. Benchmark revisions reflect a re-anchoring of CES sample-based estimates to incorporate near universe counts of employment. These comprehensive counts of employment, or benchmarks, are derived primarily from employment counts reported on UI tax reports that nearly all employers are required to file with State Workforce Agencies.