The Bay Area Equity Atlas (referred to simply as the “Atlas” below) draws upon a regional equity indicators database assembled using a broad array of data sources and methodologies. The data not only is drawn from the National Equity Atlas indicators database, also developed and maintained by PolicyLink and ERI, but also includes more than a dozen new indicators derived from local and state data sources as well as unique surveys. The Atlas includes data for the following geographies:
- Region: The Five- and Nine-County Bay Area regions
- County: The nine Bay Area counties (Alameda, Contra Costa, Marin, Napa, San Mateo, San Francisco, Santa Clara, Solano, and Sonoma)
- Sub-county: 40 Consistent Public Use Microdata Areas (CPUMAs)
- Large city: Six large Bay Area cities (Fremont, Hayward, Oakland, San Francisco, San José, and Sunnyvale)
- Other city or town: 95 other Bay Area cities and towns
- Census Designated Place (CDP): 119 unincorporated areas of Bay Area counties identified by the Census for statistical purposes
- State: California
The Atlas also includes data in some maps for the 1,588 census tracts in the region. While indicator data is available for a variety of years from 2000 onward, it was derived to reflect consistent geographic boundaries over time. While some geographies, such as counties, tend to be fairly stable over time, others, such as census-defined places and census tracts, are not and can change with each decennial census. Data for counties (and thus the five- and nine-county regions), census-defined places and census tracts reflect the official geographic boundaries of the 2010 Decennial Census (although there have been no county boundary changes in the region since 2000).
Consistent Public Use Microdata Areas (referred to as “CPUMAs” in the Atlas) are a geography created by the Integrated Public Use Microdata Series (IPUMS USA). The version used in the Atlas is based on the CPUMA0010 variable and is drawn to essentially form what is the lowest common denominator from a geographic perspective between 2000 and 2010 Public Use Microdata Areas (PUMAs). PUMAs are statistical geographic areas of at least 100,000 people and are defined for the dissemination of Public Use Microdata Sample (PUMS) data from the Decennial Census and American Community Survey (ACS).
Although a variety of state and local data sources are used, the summary and microdata files from the long form (Summary File 3) of the 2000 Census and from the ACS for years 2010 and later are the primary data sources, and account for a large portion of the indicators and breakdowns found in the Atlas. Given the detailed ways in which the Atlas cuts data by geography and social and demographic characteristics, we selected versions of the summary and microdata files to achieve a large enough sample size for a reasonable degree of statistical reliability. For example, Summary File 3 of the 2000 Census includes a sample of about one in six households, and the microdata files are available as both 1- and 5-percent samples of the U.S. population. We chose the 2000 5-percent sample. The ACS replaced the long form of the Decennial Census in 2010, and is an annual survey that is administered continuously throughout each year covering about 1 percent of the U.S. population each year. The data are currently released as both 1-year and 5-year samples, and we use the 5-year samples to achieve a comparable sample size to that in 2000.
There is a tradeoff between the summary files and microdata in terms of the level of detail of the social and demographic characteristics that can be tabulated, and the level of detail in terms of geography. The summary files of the Decennial Census and ACS include a limited set of summary tabulations of population and housing characteristics and are available at a high level of geographic detail (down to what is known as the census block group level), while the microdata (or PUMS) files contain individual responses to these respective surveys, allowing for great flexibility in terms of the characteristics that can be tabulated, but they can only be tabulated down to the PUMA level.
To strike a balance between providing some data for all Atlas geographies for as many indicators as possible — including smaller geographies such as census-defined places and census tracts — and providing data by detailed demographic categories such as race/ethnicity, gender, ancestry, and poverty level, we draw upon both the summary and microdata files for many indicators. In general, we use the Census and ACS summary files for certain breakdowns (e.g., trends, rankings, maps) that cover all Atlas geographies but are not highly detailed in terms of demographic categories, and draw upon Census and ACS microdata for other breakdowns that are not available for the smallest Atlas geographies (e.g., other city or town, census designated place, and census tract) but provide indicator data by far more detailed demographic categories.
Details on the data sources and methods used for each indicator can be found by clicking on the People, Place, and Power indicator category links at the bottom of this page. However, a few notes on dataset construction are relevant to many indicators and are worth noting here; most are related to how the Census and ACS summary files and microdata are applied.