In 2003, the Census Bureau produced county-to-county migration flow files based on the Census 2000 long-form question on residence five years earlier. These files are available below. With 3,141 counties in 2000, there were over 9 million combinations of county-to-county migration flows nationwide. The county-to-county migration flow files made it relatively straightforward to see local migration dynamics, but it is more challenging to detect broader migration trends. Tables presented here have aggregated the county-to-county flows into metro area-to-metro area flows, which are presented with extensive hyperlinks for making comparisons across a broad range of areas. The six tables listed below show migration totals for all metro areas sorted by title, total metropolitan population, gross migration, gross migration rate, net migration, and net migration rate. Clicking on a metro area title navigates to a page displaying that metro area's migration flows with each metro area. That page also includes a summary of the migration flows between that metro area and all other metro areas, as well as outside metro areas.

Inmigrants - People who resided in a particular metropolitan statistical area in 2000, but who reported a place of residence in 1995 that was outside that metropolitan statistical area.

Outmigrants - People who reported a place of residence in 1995 that was inside a particular metropolitan statistical area, but who resided outside that metropolitan statistical area in 2000.

Gross Migration - The sum of the number of inmigrants and the number of outmigrants for a given metropolitan statistical area between 1995 and 2000.

Gross Migration Rate - The sum of the number of inmigrants and the number of outmigrants for a given metropolitan statistical area in the five-year period prior to the decennial census, per 1,000 population in 1995. The gross migration rate is based on an approximated 1995 population, which is the sum of people who reported living in the area in both 1995 and 2000, and those who reported living in that area in 1995 but lived elsewhere in 2000. The gross migration rate is the 1995-to-2000 gross migration, divided by the approximated 1995 population and multiplied by 1000.

Net Migration - The difference between the number of inmigrants and the number of outmigrants for a given metropolitan statistical area between 1995 and 2000. A positive net, or net inmigration, indicates that more migrants entered the area than left the area during that time. A negative net, or net outmigration, indicates that more migrants left the area than entered it.

Net Migration Rate - The difference between the number of inmigrants and the number of outmigrants for a given metropolitan statistical area in the five-year period prior to the decennial census, per 1,000 population in 1995. The net migration rate is based on an approximated 1995 population, which is the sum of people who reported living in the area in both 1995 and 2000, and those who reported living in that area in 1995 but lived elsewhere in 2000. The net migration rate is the 1995-to-2000 net migration, divided by the approximated 1995 population and multiplied by 1000. A positive figure is known as a net inmigration rate and a negative figure as a net outmigration rate.

Migration Efficiency - A measure of the relationship between a migration flow and its reverse flow for a pair of areas. Defined as net migration per 100 gross migration, its value ranges from -100 to +100, with zero indicating equal flows in both directions.

Metropolitan Statistical Area - Geographic entities defined by the U.S. Office of Management and Budget (OMB) for use by federal statistical agencies in collecting, tabulating, and publishing federal statistics. A metro area contains a core urban area of 50,000 or more population. Each metro area consists of one or more counties and includes the counties containing the core urban area, as well as any adjacent counties that have a high degree of social and economic integration (as measured by commuting to work) with the urban core.

The metropolitan statistical areas in these tables use the June 2003 OMB definitions. The codes, titles, and county components for all metropolitan statistical areas as of June 2003 are available below. In some instances, the title of the metropolitan statistical area has been truncated in the column headings.

In the June 2003 OMB definition, Broomfield County, Colorado is included in the Denver-Aurora, CO Metropolitan Statistical Area. In the county-to-county migration flow files, however, counties are bounded as they existed on April 1, 2000, the date of Census 2000. Because Broomfield County (08-014) was created on November 15, 2001 (from parts of Adams (08-001), Boulder (08-013), Jefferson (08-059), and Weld (08-123) counties), it is not represented in the county-to-county or metro-to-metro files. For the metro area-to-metro area migration tables, Adams and Jefferson counties, which include parts of Broomfield city, are included in the Denver-Aurora, CO Metropolitan Statistical Area, but the parts of Broomfield city that had been in Boulder and Weld counties are not included in the Denver-Aurora, CO metro area; Boulder County, including that part of Broomfield city that had been in Boulder County, comprises the Boulder, CO Metropolitan Statistical Area; and Weld County, including that part of Broomfield city that had been in Weld County, comprises the Greeley, CO Metropolitan Statistical Area.

The metro area-to-metro area migration figures are based on sample data. The primary sources of error and the programs instituted to control error in Census 2000 are described in detail in Summary File 3 Technical Documentation under Chapter 8, "Accuracy of the Data," listed below.

The metro area-to-metro area migration figures presented here are based on the Census 2000 question on residence in 1995. Question 15a on the Census 2000 long form asked for the population five years and older, "Did this person live in this house or apartment 5 years ago (on April 1, 1995)?" If "No, different house in the United States" was selected, the respondent was asked in question 15b, "Where did this person live 5 years ago?" with blanks provided to fill in the "city, town, or post office," as well as county, state, and ZIP Code.

The metro area-to-metro area migration figures were aggregated from the County-to-County Migration Flow Files available on the County-to-Migration Flows page listed below.