1950 "sample line persons under age 30"

In the 1950 data the Universe stipulates that the “school” item is asked of “sample line persons under age 30.” What does this mean? When I restrict the age range in 1950 to 15 to 24-year-olds I have nearly 77% missing or N/A responses. Was the sample asked the school question restricted somehow?

Sample line persons refers to a specific subsample of persons who were asked a full set of supplemental questions in the 1950 census (and 1940). You can learn more about “sample line persons” in the 1950 (and 1940) on our sample designs page. The variable SLREC can be used to identify if the individual record is the sample-line person.