Number of Jobs Held, Labor Market Activity, and Earnings Growth Among the Youngest Baby Boomers: Results From a Longitudinal Survey Technical Note

                                  - 4 -

Technical Note
  
  
  
  The estimates in this release were obtained using data from the first 
21 rounds of the National Longitudinal Survey of Youth 1979 (NLSY79).  This
survey is conducted by the Center for Human Resource Research at The Ohio
State University and the National Opinion Research Center at the University
of Chicago under the direction and sponsorship of the U.S. Department of
Labor's Bureau of Labor Statistics.

Sample
  
  The NLSY79 is a nationally representative sample of 12,686 young men and
women who were 14 to 22 years of age when first surveyed in 1979.  This
survey sample was initially composed of three subsamples:
  
   --A cross-sectional sample of 6,111 youths that was designed to represent 
the noninstitutionalized, civilian population of young people living in the 
U.S. in 1979 and born between January 1, 1957, and December 31, 1964
   
   --A supplemental sample of 5,295 youths designed to oversample noninstitu-
tionalized, civilian black, Hispanic or Latino, and economically disadvantaged 
nonblack, non-Hispanic youths living in the U.S. in 1979 and born between 
January 1, 1957, and December 31, 1964
   
   --A military sample of 1,280 youths born between January 1, 1957, and 
December 31, 1961, and enlisted in the Army, Air Force, Navy, or Marine Corps 
as of September 30, 1978
  
  In 1985, the military sample was discontinued, and, in 1991, the econom-
ically disadvantaged nonblack, non-Hispanic youths were dropped from the 
supplemental sample.  As a result, the NLSY79 sample now includes 9,964 in-
dividuals from the cross-sectional sample and the black and Hispanic or La-
tino supplemental samples.  (This sample size is not adjusted for sample 
members who have died.)
  
  Individuals were surveyed annually from 1979 to 1994 and biennially
since 1994.  In 2004-05, 7,661 individuals responded to the survey, for a
retention rate of 77 percent.  Only these individuals are included in the
estimates in this release.  All results are weighted using the 2004-05 sur-
vey weights that correct for the oversampling, interview nonresponse, and 
permanent attrition from the survey.  When weighted, the estimates represent 
all persons born in the years 1957 to 1964 and living in the U.S. when the 
survey began in 1979.  Not represented by the survey are U.S. immigrants 
who were born from 1957 to 1964 and moved to the United States after 1979.
                                  
                                  - 5 -

Work history data
  
  The total number of jobs that people hold during their work life is an
easy concept to understand but a difficult one to measure.  Reliable esti-
mates require a survey that interviews the same people over the course
of their entire work life and also keeps track of all the jobs they ever
held.  The NLSY79 tracks the number of jobs that people have held, but the
respondents in this survey are still relatively young, ages 39 to 48 in
2004-05, and have many years of work life ahead of them.  As the cohort con-
tinues to age, however, more complete information will become available.
  
  A unique feature of the NLSY79 is that it collects the beginning and
ending dates of all jobs held by a respondent so that a longitudinal
history can be constructed of each respondent's work experiences.  The
NLSY79 work history data provide a week-by-week work record of each re-
spondent from January 1, 1978, through the most recent survey date.  These
data contain information on the respondent's labor force status each week,
the usual hours worked per week at all jobs, and earnings for all jobs.  
If a respondent worked at more than one job in any week, hours and earnings
are obtained for additional jobs.  When a respondent who missed one or more 
consecutive survey rounds is interviewed again, he is asked to provide in-
formation about all time since the last interview.

Interaction between time and age in a longitudinal survey
  
  Because the NLSY79 is a longitudinal survey, meaning the same people 
are surveyed over time, the ages of the respondents change with each sur-
vey round.  It is important to keep in mind this inherent link between the
calendar years and the ages of the respondents.  For example, table 5 re-
ports earnings growth from age 22 to age 25.  The youngest respondents in
the sample (birth year 1964) were these ages during 1986-89, whereas the
oldest respondents (birth year 1957) were these ages during 1979-82.
  
  Although participants in the NLSY79 were ages 39 to 48 during the 2004-05
interviews, this release cover only the period while the respondents were 
ages 18 to 40.  The reason for not including older ages is that the sample 
sizes were still too small to provide statistically reliable estimates for 
age groups older than 40.  As the NLSY79 continues to be administered and 
the respondents age, subsequent rounds of the survey will enable analyses 
to be conducted for older age groups.
  
  As with age, the educational attainment of individuals may change from
year to year.  In the tables and analysis presented in this report, edu-
cational attainment is defined as of the 2004-05 survey.  This definition
is used even when data on age and educational attainment are presented
together.  For example, table 1 reports the number of jobs held during
different age categories.  Suppose that a respondent had completed a
bachelor's degree at age 28.  That respondent would be included in the
"Bachelor's degree and higher" educational category in all age categories
shown on the table, even though he or she did not have a bachelor's 
degree at any point from age 18 to age 27.

                                  - 6 -

Definitions
  
  Job.  A job is defined as an uninterrupted period of work with a
particular employer.  Jobs are therefore employer-based, not position-
based.  If a respondent indicates that he or she left a job but in a
subsequent survey returned to the same job, it is counted as a new job.
For example, if an individual worked in a retail establishment during the
summer, quit at the end of summer to return to school, and then resumed
working for the same employer the following spring, this sequence would
count as two jobs, rather than one.  For self-employed workers, each "new"
job is defined by the individuals themselves.
  
  Unemployment.  If respondents indicate a gap between employers, they are
asked how many of those weeks they spent searching for employment or on
layoff.  For that number of weeks, they are considered unemployed.  For the
remaining weeks, they are coded as not in the labor force.  No probing for
intensity of job search is done.
  
  Usual earnings.  Respondents can report earnings over any time frame
(hour, day, week, month, year).  For those who do not report an hourly
wage, one is constructed using usual hours worked over that time frame.
Wages greater than $100 per hour and less than $1 per hour were not in-
cluded in the analysis of earnings growth because the reported earnings
levels were almost certainly in error.  For the same reason, individuals
who had inflation-adjusted earnings growth greater than 100 percent were
not included in the analysis.  These exclusions from the analysis af-
fected 98 respondents.
  
  Race and ethnicity groups.  In this release, the findings are reported for
non-Hispanic whites, non-Hispanic blacks, and Hispanics or Latinos.  These 
three groups are mutually exclusive but not exhaustive.  Other race groups, 
which are included in the overall totals, are not shown separately because 
their representation in the survey sample is not sufficiently large to pro-
vide statistically reliable estimates.  In other BLS publications, estimates
usually are published for whites, blacks, and Hispanics or Latinos, but these 
groups are not mutually exclusive.  The terms "Hispanic or Latino" are consi-
dered to be an ethnicity group, and Hispanics or Latinos can be of any race.  
Most other BLS publications include Hispanics or Latinos in the white and 
black race groups in addition to the Hispanic or Latino ethnicity group.
  
  Information in this release will be made available to sensory impaired in-
dividuals upon request.  Voice phone:  202-691-5200; TDD message referral
phone:  1-800-877-8339.