Commentary: continuous work history sample.

The Continuous Work History Sample (CWHS) is the oldest major continuous longitudinal sample data source in the Federal statistical system. It was developed to fulfill the need for statistics to be used in planning and operating the old-age insurance system established by the Soda1 Security Act of 1935. This Act led to the establishment of one of the most extensive sets of administrative records in the world. Before the 1930’s, there was very little national information on earnings and employment. What existed was collected by various government agencies, crosssectional in nature, and limited to a particular time period with no ability to trace an individual’s earnings over a long time span. The need for statistics on the continuity of earnings and employment data became urgent during the 1930’s when widespread unemployment became a serious economic problem with significant policy implications. Several surveys were made using interviews to obtain work histories. For the most part these surveys were limited in coverage and were based on the memory of individuals being interviewed, which cannot be relied on for accurate wage and employment information over long periods of time. With the enactment of the