The data on residence 1 year ago were derived from answers to Question 14a, 14b, and 14c, which were asked of the population 1 year and older. For the American Community Survey, people who had moved from another residence in the United States or Puerto Rico 1 year earlier were asked to report the exact address (number and street name); the name of the city, town, or post office; the name of the U.S. county or municipio in Puerto Rico; state or Puerto Rico; and the ZIP Code where they lived 1 year ago. People living outside the United States and Puerto Rico were asked to report the name of the foreign country or U.S. Island Area where they were living 1 year ago.
For the Puerto Rico Community Survey, people who moved from another residence in Puerto Rico or the United States 1 year ago were asked to report the exact address, including the development or condominium name; the name of the city, town, or post office; the municipio in Puerto Rico (county equivalent) or county in the U.S.; and the ZIP Code where they lived. People living outside Puerto Rico and the United States were asked to report the name of the foreign country or U.S. Island Area where they were living 1 year ago.
Residence 1 year ago is used in conjunction with location of current residence to determine the extent of residential mobility of the population and the resulting redistribution of the population across the various states, metropolitan areas, and regions of the country.
When no information on previous residence was reported for a person, information for other family members, if available, was used to assign a location of residence 1 year ago. All cases of nonresponse or incomplete response that were not assigned a previous residence based on information from other family members were allocated the previous residence of another person with similar characteristics who provided complete information.
The tabulation category, "Same house," includes all people 1 year and over who did not move during the 1 year as well as those who had moved and returned to their residence 1 year ago. The category, "Different house in the United States" includes people who lived in the United States 1 year ago but in a different house or apartment from the one they occupied at the time of interview. These movers are then further subdivided according to the type of move.
In most tabulations, movers within the U.S. are divided into three groups according to their previous residence: "Different house, same county," "Different county, same state," and "Different state." The last group may be further subdivided into region of residence 1 year ago. An additional category, "Abroad," includes those whose previous residence was in a foreign country, Puerto Rico, American Samoa, Guam, the Northern Marianas, or the U.S. Virgin Islands, including members of the Armed Forces and their dependents. Some tabulations show movers who were residing in Puerto Rico or one of the U.S. Island Areas 1 year ago separately from those residing in foreign countries.
In most tabulations, movers within Puerto Rico are divided into two groups according to their residence 1 year ago: "Same municipio," and "Different municipio." Municipio of previous residence in Puerto Rico is not available for people living in the United States in 2005. Other tabulations show movers within or between metropolitan areas similar to the stateside tabulations.

State legislative districts (SLDs) are the areas from which members are elected to state legislatures. The SLDs embody the upper (senate) and lower (house) chambers of the state legislature. (Nebraska has a unicameral legislature that the U.S. Census Bureau treats as an upper-chamber legislative area for data presentation purposes. There are, therefore, no data by lower chamber.) A unique census code of up to three characters, identified by state participants, is assigned to each SLD within state. The code "ZZZ" identifies parts of a county in which no SLDs were identified. As an option in the Census 2000 Redistricting Data Program (Public Law 94-171), participating states receive P.L. 94-171 census data for their SLDs (see VOTING DISTRICT (VTD)). Not all states delineated SLDs for the purpose of presenting Census 2000 data, in which case the entire state is treated as a single SLD coded with blanks at both levels.

The primary legal divisions of most states are termed "counties." In Louisiana, these divisions are known as parishes. In Alaska, which has no counties, the statistically equivalent entities are census areas, city and boroughs (as in Juneau City and Borough), a municipality (Anchorage), and organized boroughs. Census areas are delineated cooperatively for data presentation purposes by the state of Alaska and the U.S. Census Bureau. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places that are independent of any county organization and thus constitute primary divisions of their states; these incorporated places are known as "independent cities" and are treated as equivalent to counties for data presentation purposes. (In some data presentations, they may be treated as county subdivisions and places.) The District of Columbia has no primary divisions, and the entire area is considered equivalent to a county for data presentation purposes. In American Samoa, the primary divisions are districts and islands; in the Northern Mariana Islands, municipalities; in the Virgin Islands of the United States, the principal islands of St. Croix, St. John, and St. Thomas. Guam has no primary divisions, and the entire area is considered equivalent to a county for data presentation purposes.

Each county and statistically equivalent entity is assigned a three-digit Federal Information Processing Standards code that is unique within state. These codes are assigned in alphabetical order of county or county equivalent within state, except for the independent cities, which are assigned codes higher than and following the listing of counties.

Places, for the reporting of decennial census data, include census designated places, consolidated cities, and incorporated places. Each place is assigned a five-digit Federal Information Processing Standards (FIPS) code, based on the alphabetical order of the place name within each state. If place names are duplicated within a state and they represent distinctly different areas, a separate code is assigned to each place name alphabetically by primary county in which each place is located, or if both places are in the same county, alphabetically by their legal description (for example, "city" before "village" ).

The U.S. Census Bureau treats the Commonwealth of Puerto Rico as the statistical equivalent of a state for data presentation purposes. Each state and statistically equivalent entity is assigned a two-digit Federal Information Processing Standards (FIPS) code in alphabetical order by state name, followed in alphabetical order by Puerto Rico and the Island Areas. Each state and statistically equivalent entity also is assigned the two-letter FIPS/U.S. Postal Service code.