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Decennial Census

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Subject Matter Comparability

Comparability With Different Decennial Censuses

2000 - 2010. The short-form questionnaire for the 2010 Census was very similar to the short-form questionnaire for the 2000 Census. Therefore, most data available from the 2010 Census can be reliably compared with the short-form data from the 2000 Census. There were some less substantial changes between the 2000 and 2010 censuses that may affect some analysis. Please see Details on Comparability of 2010 Census Data for more information on comparing 2010 Census data with short-form data from the 1990 and 2000 censuses.

1990 - 2000. Some substantial changes to the short-form were made for the 2000 Census which affects comparability with 1990 Census data.

The changes in 2000 include:

  • Ethnicity asked before race (and identified as "Hispanic or Latino")
  • Respondents could select one or more races
  • Asian and Pacific Islander category split ("Asian" or "Native Hawaiian and Other Pacific Islander")

The allowance of multiple race responses makes it difficult to obtain direct comparability to 1990 and earlier censuses.

Comparability With the American Community Survey

The biggest change in subject matter for the 2010 Census is the lack of long-form questionnaire data. The traditional long-form questionnaire was eliminated in 2010 and has been replaced with the American Community Survey. This change presents a number of challenges. While the ACS provides data on a more frequent basis, the questions and time-frames are different. Therefore comparing the ACS data to the 2000 Census long-form data can be difficult. For more details, see the table-specific guidance from the Census Bureau on making comparisons using ACS data.

Geographic Comparability

When comparing data by a geographic area, please be aware that the Census Bureau redraws the geography every ten years based on physical changes such as new streets or a change in population. There were a number of changes in the census geography in Seattle for both the 2000 and 2010 Censuses. Please see Data Issues under Geographc Files and Maps.

Locally-Defined Neighborhoods

In order to report census data for neighborhood areas, we use different combinations of census tracts, block groups, and blocks to best approximate the various neighborhoods and sub-areas of Seattle. There are a few minor changes to the underlying blocks, block groups, and tracts in the 2010 geography that may affect the geographic area designated as a particular neighborhood. Changes observed in census data between decennial censuses may be affected by these changes in geography.

Changes in geography also affect comparing numbers from previously published reports to newer reports from the 2010 Census data. Neighborhood boundaries as well as the census geography that represent them change over time; previously published Census 2000 reports have not been updated to use consistent boundaries. Some changes in the data may be related to these geographic changes. Please refer to the provided neighborhood reference maps to identify significant changes in geography.

Derived Measures

The Census Bureau does not provide data or derived measures such as medians and averages for aggregations of census geography. Derived measures for these areas were estimated by the City of Seattle.

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