The data on place of birth were derived from answers to long-form questionnaire Item 12 which was asked of a sample of the population. Respondents were asked to report the U.S. state, Puerto Rico, U.S. Island Area, or foreign country where they were born. People not reporting a place of birth were assigned the state or country of birth of another family member or their residence 5 years earlier, or were imputed the response of another person with similar characteristics. People born outside the United States were asked to report their place of birth according to current international boundaries. Since numerous changes in boundaries of foreign countries have occurred in the last century, some people may have reported their place of birth in terms of boundaries that existed at the time of their birth or emigration, or in accordance with their own national preference.
The place of birth question for residents of Puerto Rico was identical to the question on the stateside questionnaires. The same code lists were used to code the responses and similar edits were applied.
Information on place of birth and citizenship status was used to classify the population into two major categories: native and foreign born. (See "Native" and "Foreign Born" under "Citizenship Status.")
The 2000 decennial census place of birth question matches the 1999 and subsequent American Community Survey (ACS) questions. The 1990 decennial census place of birth question matches the 1996-1998 ACS questions. For the 2000 decennial census and post-1998 ACS samples, separate check boxes and write-in spaces were used for people born in the United Sates and those born outside the United States.
Data on place of birth have been collected in each U.S. census since 1850. In prior censuses, the place of birth question asked respondents to report the state or foreign country where they were born. There were no check boxes in prior censuses. Nonresponse to the place of birth question has been imputed to some degree since 1970. For 1970 through 1990, state of birth was imputed for people born in the United States; people born outside the United States were assigned "born abroad, country not specified" or "born in an outlying area, not specified." In 2000, a specific Island Area (referred to as "outlying areas" in previous censuses) or country of birth was imputed.
Data on place of birth for Puerto Rico was asked beginning in 1910. In censuses prior to 2000, the place of birth question asked respondents to report the municipio in Puerto Rico as well as the U.S. state or the foreign country where they were born. Tabulations for those censuses showed people who were born in the same or a different municipio. Municipio of birth was not asked in 2000. Nonresponse was imputed in 1980 and 1990 for all questions, but a specific foreign country was not imputed until 2000.
Parental nativity (birthplace of parents) was asked of a sample of the population in each decennial census between 1870 and 1970. The 1980, 1990, and 2000 decennial censuses instead included a question on ancestry, except for the U.S. Island Areas (such as Guam) which asked the parental nativity question. (See "Ancestry.")