Technical Note The estimates in this release were obtained using data from the first 25 rounds of the National Longitudinal Survey of Youth 1979 (NLSY79). This sur- vey is conducted by the National Opinion Research Center at the University of Chicago and the Center for Human Resource Research at The Ohio State University under the direction and sponsorship of the U.S. Department of Laborís 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 sur- vey 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 Jan. 1, 1957, and Dec. 31, 1964. --A supplemental sample of 5,295 youths designed to oversample noninsti- tutionalized, civilian black, Hispanic or Latino, and economically dis- advantaged nonblack, non-Hispanic youths living in the U.S. in 1979 and born between Jan. 1, 1957, and Dec. 31, 1964. --A military sample of 1,280 youths born between Jan. 1, 1957, and Dec. 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 economic- ally disadvantaged nonblack, non-Hispanic youths were dropped from the sup- plemental sample. As a result, the NLSY79 sample now includes 9,964 individ- uals from the cross-sectional sample and the black and Hispanic 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 2012-13, 7,301 individuals responded to the survey, for a retention rate of 73 percent (representing a 79 percent response rate among those sample members who are still living). Only these individuals are included in the estimates in this release. All results are weighted using the 2012-13 survey 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 U.S. after 1979. 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 most of the respondents in this survey are still in their prime working years, ages 47 to 56 in 2012-13, and still have more years of work life ahead of them. As the cohort continues to age, however, more complete information will become available. A unique feature of the NLSY79 is that it collects the beginning and end- ing dates of all jobs held by a respondent so that a longitudinal history can be constructed of each respondentís work experiences. The NLSY79 work history data provide a week-by-week work record of each respondent from Jan. 1, 1978, through the most recent survey date. These data contain in- formation on the respondentís 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 information 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 25 to age 29. The youngest respondents in the sample (birth year 1964) were these ages during 1989-93, whereas the oldest respondents (birth year 1957) were these ages during 1982-86. Although participants in the NLSY79 were ages 47 to 56 during the 2012- 13 interviews, this release covers only the period while the respondents were ages 18 to 46. The reason for not including older ages is that the sample sizes were still too small to provide statistically reliable esti- mates for age groups older than 48. As the NLSY79 continues to be adminis- tered 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, educa- tional attainment is defined as of the 2012-13 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 bachelorís degree at age 40. That respondent would be included in the "Bachelorís degree or more" educational category in all age categories shown on the table, even though he or she did not have a bachelorís degree at any point from age 18 to age 39. Definitions Job. A job is defined as an uninterrupted period of work with a particu- lar 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, ra- ther 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 (in January 1979 dollars, 100=283.70 in December 2010 dollars) were not included 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 affected 37 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 provide statistically reliable estimates. In other BLS publica- tions, estimates usually are published for whites, blacks, and Hispanics or Latinos, but these groups are not mutually exclusive. The term "His- panic or Latino" is considered to be an ethnicity group, and Hispanics or Latinos can be of any race. Most other BLS publications include Hispan- ics or Latinos in the white and black race groups in addition to the His- panic or Latino ethnicity group. Information in this release will be made available to sensory impaired individuals upon request. Voice phone: (202) 691-5200; Federal Relay Ser- vice: (800) 877-8339.