- The U.S. Census is taken once every ten years, in years ending with "0." It includes information from the last completed year, such as income reported in tax returns. Census information is confidential. No one outside the Bureau of the Census, including other government agencies, is allowed access to recent individual census forms. Such access is granted only after 72 years have passed. However, data aggregated by Census block groups and Census tracts is made available, usually three to four years after completion of the Census.
- Level of aggregation: Census Tract and Census Block Group.
- The variable names are the codes used by the Census to identify its variables. The codes and their translation are available in a data dictionary.
- There are 168 Census Tracts and 630 Census Block Groups in Boston.
- "STF1" refers to Summary Tape File 1. This file consists of responses of persons completing the short Census form or its equivalent. This is presumably a count of all persons, or a 100 % count.
- "STF3" refers to Summary Tape File 3. This file consists of a survey of approximately one out of every six persons (17%). The actual number and percentage of people in an area who are surveyed varies according to how homogeneous the population is. These households were asked to complete a longer, more detailed Census questionnaire from which this data is taken.
- "Household" A household includes all the persons who occupy a housing unit. A housing unit is a house, an apartment, a mobile home, a group of rooms, or a single room that is occupied (or if vacant, is intended for occupancy) as separate living quarters. Separate living quarters are those in which the occupants live and eat separately from any other persons in the building and which have direct access from the outside of the building or through a common hall. The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated persons who share living arrangements. In 100-percent tabulations [STF1], the count of households or householders always equals the count of occupied housing units. In sample tabulations [STF3], the numbers may differ as a result of the weighting process. From Census Documentation
- "Race" and "Hispanic Origin" People answer the questions on Race and Hispanic Origin depending on how they identify themselves. These are two distinct categories and should not be added together since that will result in double-counting. A person can identify him or herself as belonging to a particular race AND identify him or herself as being Hispanic. For example, a person can be both Asian/Pacific Islander AND Hispanic.
- Variables designated under Variable Description as [STF1], that is columns B through BL, are from the STF1 Census files, or the 100% sample. All other variables, columns BM through BV, are from the STF3 Census files, or the 17% sample.