CES Birth/Death Model Frequently Asked Questions
- Do the birth/death factors vary from first preliminary to final estimate?
No, the birth/death factor for a given month does not change between first preliminary, second preliminary, and final sample-based estimates. However, the birth/death factors used in the reestimated values from April of the benchmark year to December of the benchmark year are updated during the benchmarking process to reflect newly forecasted birth/death values.
- Are birth/death factors seasonally adjusted?
No, they are calculated using population data that is not seasonally adjusted and the factors are applied to the sample-based not seasonally adjusted estimates. Months with generally strong seasonal increases such as April, May, and June generally have a relatively large positive factor. Conversely, months with overall strong seasonal decreases, such as January, generally have a relatively large negative factor.
- Can I subtract the birth/death adjustment from the seasonally adjusted over-the-month change to determine what it is adding to employment?
No. Birth/death factors are a component of the not seasonally adjusted estimate and, therefore, are not directly comparable to the seasonally adjusted monthly changes. Instead, the birth/death factor should be assessed
in the context of its effect on the not seasonally adjusted estimate.
- Can BLS provide an estimate of the contribution of the birth/death adjustment to the seasonally adjusted monthly payroll change?
BLS does not calculate an estimate of the seasonally adjusted contribution of the birth/death model. The sample, the imputation of business births using deaths, and the net birth/death model are all necessary components for obtaining an accurate total employment estimate. The components are not seasonally adjusted separately because they do not have any particular economic meaning in and of themselves.
- How frequently are the birth/death figures revised and why do the values change?
Birth/death factors are revised once a year with the benchmark revision. There are two reasons that the birth/death values change with the update. First, each year additional months of data are added to the historical series used as inputs to the model. As a result of the additional data, the model provides updated results. For example, the first
preliminary estimate for June 2013 was produced on the March 2012 Benchmark using the input data
through June 2012. When the March 2013 Benchmark was implemented, the June 2013 birth/death factor was
revised to a forecast using input data through March 2013. For more information on the timing and updates
to the inputs for the birth/death forecasts, please see www.bls.gov/ces/ces_quarterly_birthdeath.pdf.
- How long has CES been using the birth/death factors and is the history of birth/death available?
Implementation of the birth/death factors was associated with the implementation of a new probability-based sample design and estimator.
The new methodology was phased in gradually under the following schedule: Beginning in June 2000 (with March 1999 Benchmark),
Wholesale Trade on an SIC-basis was under the new methodology; in June 2001 (with the March 2000 Benchmark), Mining, Construction,
and Manufacturing, on an SIC-basis, were added; in June 2002 (with the March 2001 Benchmark), all of Total Private with the exception of
Services were under the new methodology; with the conversion to NAICS in June 2003 (with the March 2002 Benchmark), all of the Total
Private industries were produced under the new methodology.
Historical Birth/Death factors are available at www.bls.gov/web/empsit/cesbdhst.htm .
- Were estimates purely sample-based before 2003?
No, prior to the implementation of birth/death modeling, CES used a technique known as bias adjustment to account for business births, business deaths, and other limitations of the survey. More information about the bias adjustment model and the CES transition to the birth/death model is available in the 2002
Benchmark Article, available here: www.bls.gov/ces/cesbmart02.pdf.
Last Modified Date: February 14, 2014