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Technical Note
  
  
   The data in this release were collected through a supplement to the 
January 2008 Current Population Survey (CPS).  The CPS, which is 
conducted by the U.S. Census Bureau for the Bureau of Labor Statistics 
(BLS), is a monthly survey of about 60,000 households that provides
information on the labor force status, demographics, and other charac-
teristics of the nation's civilian noninstitutional population age 16 
and over.
  
   The January 2008 CPS supplement obtained information on worker dis-
placement and workers' tenure with their current employer.  The data on 
worker displacement appear in the BLS news release USDL 08-1183, "Worker 
Displacement, 2005-2007," issued on August 20, 2008.

   Information in this release will be made available to sensory-impaired 
individuals upon request.  Voice phone:  (202) 691-5200, TDD message re-
ferral phone number:  1-800-877-8339.

Reliability of the estimates
 
   Statistics based on the CPS are subject to both sampling and nonsampling 
error.  When a sample, rather than the entire population, is surveyed, 
there is a chance that the sample estimates may differ from the "true" pop-
ulation values they represent.  The exact difference, or sampling error, 
varies depending on the particular sample selected, and this variability 
is measured by the standard error of the estimate.  There is about a 90-
percent chance, or level of confidence, that an estimate based on a sam-
ple will differ by no more than 1.6 standard errors from the "true" popu-
lation value because of sampling error.  BLS analyses are generally con-
ducted at the 90-percent level of confidence. The CPS data also are af-
fected by nonsampling error.  Nonsampling error can occur for many rea-
sons, including the failure to sample a segment of the population, in-
ability to obtain information for all respondents in the sample, inabil-
ity or unwillingness of respondents to provide correct information, and
errors made in the collection or processing of the data.

   For a full discussion of the reliability of data from the CPS and in-
formation on estimating standard errors, see the explanatory note for 
the household survey online at http://www.bls.gov/cps/eetech_methods.pdf.

Tenure questions and concepts

   In the January 2008 CPS supplement, questions on tenure were asked of 
all employed persons. The first question was: "How long has ... been 
working continuously for (fill in name of present employer)?"

                                _____ Days
                                _____ Weeks
                                _____ Months
                                _____ Years

For responses of "1 year" or "2 years," a follow-up question was asked:
"Could you please give the exact number of months?"

                                - 4 -

   The purpose of the follow-up question is to obtain more precise informa-
tion on workers who had been with their current employer for a relatively 
short time.  This follow-up question was included for the first time in 
the February 1996 CPS supplement on worker displacement and tenure.  CPS 
supplements that obtained information on tenure in January of 1983, 1987, 
and 1991 did not include the follow-up question.  In those surveys, re-
sponses of 1 year or more could be coded only as the nearest full year,
and responses of less than a year were coded as the nearest full month.

   Prior to January 1983, CPS supplements on tenure asked wage and salary 
workers, "When did ... start working at (his/her) present job?"  For 
wage and salary workers, the meaning of the term "job" is ambiguous.  For
example, a worker who had been employed at a particular company for 10 
years and had been promoted to a managerial position 1 year prior to the 
survey may have been counted as having 10 years or 1 year of tenure, de-
pending on whether the respondent interpreted the question to mean tenure 
with the current employer or tenure in the managerial position.  To rec-
tify this ambiguity, the wording of the question was changed in January 
1983 to specify the length of time a worker had been with his or her cur-
rent employer.  The change resulted in a break in historical comparability.

   Data refer to the sole or principal job of full- and part-time workers.  
All data exclude the incorporated and unincorporated self employed.  

Interpreting tenure data

   Data on tenure have been used as a gauge of employment security, with some 
observers regarding increases in tenure as a sign of improving security and 
decreasing tenure as a sign of deteriorating security.  However, there are 
limitations to using the data in this way.  For example, during recessions 
or other periods of declining job security, median tenure and the proportion 
of workers with long tenure could rise because less-senior workers are more 
likely to lose their jobs than are workers with longer tenure.  During periods 
of economic growth, median tenure and the proportion of workers with long 
tenure could fall because more job opportunities are available for new en-
trants to the workforce and experienced workers have more opportunities to 
change employers and take better jobs.  Tenure also could rise under im-
proving economic conditions, however, as fewer layoffs occur and good job
matches develop between workers and employers.  

   A changing age distribution among workers would also affect median tenure.  
Since older workers are more likely to have long tenure with their current 
employer than younger workers, aging baby boomers in the workforce would 
provide upward pressure on overall median tenure.