The foreign-born population is combined with the native population of foreign or mixed parentage in a single category termed foreign stock. In this report, persons of foreign stock are classified according to their country of origin. Natives of foreign parentage whose parents were born in different countries are classified according to the country of birth of the father. Natives of mixed parentage are classified according to the country of birth of the foreign-born parent. The classification by country of origin is based on international boundaries as recognized by the United States Government on April 1, 1960, although there may have been some deviation from the rules where respondents were unaware of changes in boundaries or jurisdiction.