The data on years of school completed were derived from the answers to the two questions: (a) What is the highest grade (or year) of regular school he has ever attended? and (b) Did he finish this grade (or year)? Enumerators were instructed to obtain the approximate equivalent grade in the American school system for persons whose highest grade of attendance was in a foreign school system, whose highest (Note: the text in the original document is not clearly visible) graded school, whose highest level of schooling was measured by readers, or whose training by a tutor was regarded as qualifying under the regular school definition. Persons were to answer NOto the second question if they were attending school, had completed only part of a grade before they dropped out, or failed to pass the last grade attended.

In order to obtain data on Spanish- and Mexican/Americans for areas of the United States where most of them live, white persons (and white heads of households) of Spanish surname were distinguished separately in five Southwestern States (Arizona, California, Colorado, New Mexico, and Texas). In all other States, Puerto Rican persons (and heads of households) were identified. Puerto Rican comprise persons born in Puerto Rico and persons of native parentage with at least one parent born in Puerto Rico.