- 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.
- "Family" A family consists of a householder and one or more other persons living in the same household who are related to the householder by birth, marriage, or adoption. All persons in a household who are related to the householder are regarded as members of his or her family. A household can contain only one family for purposes of census tabulations. Not all households contain families since a household may comprise a group of unrelated persons or one person living alone. Families are classified by type as either a "married-couple family" or "other family" according to the sex of the householder and the presence of relatives. The data on family type are based on answers to questions on sex and relationship which were asked on a 100-percent basis. 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.
- "Poverty" Poverty statistics presented in census publications were based on a definition originated by the Social Security Administration in 1964 and subsequently modified by Federal interagency committees in 1969 and 1980 and prescribed by the Office of Management and Budget in Directive 14 as the standard to be used by Federal agencies for statistical purposes.
At the core of this definition was the 1961 economy food plan, the least costly of four nutritionally adequate food plans designed by the Department of Agriculture. It was determined from the agriculture Department's 1955 survey of food consumption that families of three or more persons spend approximately one-third of their income on food; hence, the poverty level of these families was set at three times the cost of the economy food plan. For smaller families and persons living alone, the cost of the economy food plan was multiplied by factors that were slightly higher to compensate for the relatively larger fixed expenses for these smaller households.
The poverty thresholds are revised annually to allow for changes in the cost of living as reflected in the Consumer Price Index. The average poverty threshold for a family of four persons was $12,674 in 1989... Poverty thresholds were applied on a national basis and were not adjusted for regional, State or local variations in the cost of living. For a detailed discussion of the poverty definition, see U.S. Bureau of the Census, Current Population Reports, Series P-60, No. 171, Poverty in the United States: 1988 and 1989. From Census Documentation