Data on years of school completed are derived from two questions, one identifying the highest grade attended in regular school (see School Enrollment); the second determining whether the respondent finished the grade specified. These data were collected on a sample basis.

Those persons who passed a high school equivalency examination (such as GED) were marked "12" under the highest grade attended (if they had not completed or were not enrolled in a higher grade). Schooling received in foreign schools was to be reported as the equivalent grade or year in the regular American school system.

The number tabulated in each category of years of school completed includes (a) persons who reported that they had attended the indicated grade and had finished it, (b) those who had attended but did not complete the next higher grade and (c) those still attending the next higher grade. Most tabulations of years of school completed are restricted to persons 25 years old and over, although some include persons 18 to 24 years old. Tabulations include persons in school as well as those who have completed their schooling. A typical way of reporting years of school completed is as follows:

Elementary:
       0 to 4 years
       5 to 7 years
       8 years

High School:
       1 to 3 years
       4 years

College:
       1 to 3 years
       4 or more years

Age at last birthday, i.e., number of completed years from birth to April 1, 1980, based on replies to a question on month and year of birth. This item was asked on a complete-count basis.

Because of the central importance of the data on age, the question contains redundancies. The age entry on the basic tape record is derived from the FOSDIC entries of quarter and year of birth. For those persons who do not provide this information but who do provide "age at last birthday," the census enumerator or clerk uses an equivalency table to mark the appropriate FOSDIC circles. The item "age at last birthday" is used only secondarily because of the tendency of some people, in reporting their ages, to round off to "0" or "5" (and to report even rather than odd numbers). The write-in entries of month and year of birth are requested because some people have difficulty with (and therefore skip) the FOSDIC marking system in this question.

Age is tabulated by single years of age and by many different groupings such as 5-year age groups. Basic records identify single years (and quarter years on sample basic records) to 112. Public-use microdata samples show single years and quarters to 99, and 100 years or more.