Summary File 4 (SF4) contains the sample data, which is the information compiled from the questions asked of a sample of all people and housing units.

The sample data are presented in 213 population tables (matrices) and 110 housing tables, identified with "PCT" and "HCT", respectively. Each table is iterated for 336 population groups: the total population, 132 race groups, 78 American Indian and Alaska Native tribe categories (reflecting 39 individual tribes), 39 Hispanic or Latino groups, and 86 ancestry groups.

SF 4 is released as individual files for each of the 50 states, the District of Columbia, and Puerto Rico; and for the United States. The tables (matrices) are identical for all files, but the geographic coverage differs. Data are provided down to the census tract level.

Summary File 3 consists of 813 detailed tables of Census 2000 social, economic and housing characteristics compiled from a sample of approximately 19 million housing units (about 1 in 6 households) that received the Census 2000 long-form questionnaire. Fifty-one tables are repeated for nine major race and Hispanic or Latino groups: White alone; Black or African American alone; American Indian and Alaska Native alone; Asian alone; Native Hawaiian and Other Pacific Islander alone; Some other race alone; Two or more races; Hispanic or Latino; and White alone, not Hispanic or Latino.

Summary File 3 presents data for the United States, the 50 states, the District of Columbia and Puerto Rico in a hierarchical sequence down to the block group for many tabulations, but only to the census tract levels for others. Summaries are included for other geographic areas such as Zip Code Tabulation Areas (ZCTAs^TM) and Congressional districts (106^th Congress).

Summary File 3 includes 484 population tables and 329 housing tables that are identified according to geographic coverage:

• Population (P) and Housing (H) tables are available to the block group
• Population (PCT) and Housing (HCT) tables are available to the census tract level only