Residential housing pattern measures are computed using decennial census data for 1980, 1990 and 2000 and were therefore released only after each decennial census. Residential housing pattern measures were not released more frequently because the various measures available here use geographic areas as small as census tracts or blocks as the unit of analysis which could only be provided by the decennial census. More current housing estimates along with many other demographic and economic estimates to tract and block group geographic levels are available from the American Community Survey which began in 2005.

Indexes of housing patterns (also called segregation indexes) for metropolitan areas (as defined on June 30, 1999) were calculated using data from the 1980 and 1990 Summary Tape File (STF) 1A, and Census 2000 Summary File (SF) 1. Metropolitan area indexes are based on Metropolitan Statistical Areas (MSAs) and Primary Statistical Areas (PMSAs) as defined by the Office of Management and Budget on June 30, 1999. Minor Civil Division-based MSAs and PMSAs were used in New England.

Core-Based Statistical Areas (CBSA), which were defined by OMB on June 6, 2003, include metropolitan and micropolitan statistical areas. Metropolitan and micropolitan areas defined on June 6, 2003 are calculated using Census 2000 data. Metropolitan areas consisting of metropolitan divisions were excluded from our calculations, but metropolitan divisions were included. Only micropolitan areas with at least 10 census tracts, and a minority population of at least 100 for the group in question were considered.

Place index scores were calculated using Census 2000 Summary File (SF) 1. Only places with 10 or more tracts, a total population of 10,000 or more and a minority population of at least 100 for the group in question were considered. Places, also called cities and towns, include census designated places, consolidated cities, and incorporated places (view the Geography Glossary) for more information on the definition of places and/or MSA/PMSAs as defined on June 30, 1999).

Indexes for metropolitan areas, micropolitan areas, or places with small minority populations are less reliable than those with larger ones. Random factors and geocoding errors are more likely to play a large role in determining the settlement pattern of group members when fewer members are present, causing these indexes to contain greater variability. Unless otherwise indicated, indexes were calculated using Non-Hispanic Whites as the reference group.