TECHNICAL NOTE

The Employment Cost Index (ECI) measures the change in the cost of labor, free from the influence of
employment shifts among occupations and industries. For information on survey concepts, coverage,
methods, nonresponse adjustment, and imputation see National Compensation Measures Handbook of
Methods at www.bls.gov/opub/hom/ncs/home.htm.

Sample size
Data for this reference period were collected from a probability sample of approximately 25,300
occupational observations selected from a sample of about 6,200 private industry establishments and
approximately 7,800 occupational observations selected from a sample of about 1,400 state and local
government establishments that provided data at the initial interview.

Standard errors
To assist users in ascertaining the reliability of ECI series, standard errors of all current quarter
not seasonally adjusted 3- and 12-month percent change series are also available, see
www.bls.gov/ncs/ect/ectvar.htm and the database query tool at www.bls.gov/ncs/ect/data.htm.
Standard errors provide users a measure of the precision of an estimate to ensure that it is within
an acceptable range for their intended purpose.

Historical listings
Historical listings are available at www.bls.gov/ect/#tables. The continuous occupational and
industry series listing uses the Standard Industrial Classification Manual and Occupational
Classification System series from 1975 through 2005 and the North American Industry Classification
System and Standard Occupational Classification from 2006 to the present. It provides the official
series deemed continuous after the change in classification systems. For more information on the
criteria used in defining continuous series, see the article published in the Monthly Labor Review at
www.bls.gov/opub/mlr/2006/04/art2full.pdf.

Employer Costs for Employee Compensation data
The costs per hour worked of compensation components are published as part of the Employer Costs for
Employee Compensation news release (ECEC). The ECEC release dates are available at
www.bls.gov/schedule/news_release/ecec.htm. Historical ECEC data are available in summary documents
at www.bls.gov/ect/#tables. Since the ECEC is calculated with current employment weights rather than
the fixed weights used in computing the ECI, year-to-year changes in the cost levels usually differ
from those in the ECI.

Fixed employment weights
For additional information on the use of fixed employment weights in computing the ECI, see
www.bls.gov/opub/mlr/2016/article/introducing-2012-fixed-employment-weights-for-the-employment-cost-
index.htm

Seasonal factors
Detailed information on seasonal factors for the 2020 reference year and the revisions of historical
seasonally adjusted data for the most recent five years can be found at www.bls.gov/ncs/ect/ectsfact.htm.