Employment Cost Index 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 Survey Handbook of Methods at

Sample size

Data for the December 2017 reference period were collected from a probability sample of approximately 27,600
occupational observations selected from a sample of about 6,600 private industry establishments and
approximately 8,000 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 Employment Cost Index (ECI) series, standard errors of all
current quarter estimates except seasonally adjusted series are made available shortly after publication of the
news release, see www.bls.gov/ncs/ect/ectvar.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 that provide all ECI data are available at www.bls.gov/ect/#tables. Included among these
listings is one that provides continuous occupational and industry series. This listing uses the Standard
Industrial Classification Manual and Occupational Classification System series through 2005 and the North
American Industry Classification System and Standard Occupational Classification from 2006 to the present. It
provides the official series from the beginning of the ECI in 1975 through the current quarter. 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 in a separate news release titled "Employer
Costs for Employee Compensation" (ECEC). These releases are issued 3 months after the reference period. The
ECEC release dates are available at www.bls.gov/schedule/2018/home.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

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Last Modified Date: January 31, 2018