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Handbook of Methods National Longitudinal Surveys Calculation

National Longitudinal Surveys: Calculation

Researchers calculate various statistics from the National Longitudinal Surveys (NLS) microdata; additionally, the program calculates its own summary estimates in its annual news releases. To facilitate the calculation of estimates that are representative of the target populations (e.g., for the NLSY79, the overall U.S. population born in the years 1957–64 and living in the United States when the sample was selected in 1978), weights have been developed that appropriately combine the sample components. Data from each interview year include a weight specific to that year. When this weight is applied, the number of sample cases is translated into the number of persons in the population that those observations represent.

The assignment of individual respondent weights involves several stages, which accounts for many factors including the respondent’s probability of selection into the screening sample, nonresponse during screening, nonresponse during each round’s collection, and other random variation associated with sampling. In addition, for cohorts that contain oversamples, adjustments are made to ensure that different sample components are combined appropriately to yield population estimates. Finally, the weights are post-stratified to match national totals. Separate weights are produced for each round of collection.

These round-specific weights may be applied directly to tabulate characteristics of the full sample for a single interview year (a single collection round). For example, to compute the average hours worked in 1987 by individuals in the NLSY79 (persons born in 1957–64 and living in the United States in 1978), one simply weights the average hours worked by the 1987 sample weight. The weights are correct when used in this way.

Sometimes researchers may want to combine data from several rounds or restrict their sample to a select set of observations. For this purpose, a custom weighting program is available that allows users to restrict their sample to select years of interviews or a select set of observations. See, for example, custom weights for the NLSY97 and custom weights for the NLSY79.

Additional details about the survey weights for each NLS cohort can be found at the links below. 

Last Modified Date: May 28, 2025