Latest Census data charts population growth in California districts

On Tuesday, the U.S. Census Bureau released the data from the Bureau’s first American Community Survey (ACS) five-year survey.The data confirm California’s trend of population moving from coastal to inland areas (this movement was also documented in the Rose Institute’s report released December 8th). The tables in the linked Excel chart below show population figures for California’s counties, Congressional Districts, State Senate Districts, and Assembly Districts. Links below also present the data for each level of geography using interactive online maps.The American Community Survey is the Bureau’s replacement for the traditional decennial Census “long form.”  The ACS includes questions about ancestry, citizenship, language spoken at home, income, and a wide variety of other demographics.

The five-year estimates are the latest set of data from the American Community Survey program, which also release data collected in one-year and three-year increments. As more years are included in the survey, the data are released at smaller levels of geography. So one-year data are only available for jurisdictions (cities and counties) over 60,000 in population. Three-year data are only available for jurisdictions over 20,000 in population. Five-year data, in contrast, are available down the level of census tracts and census block groups. Most important, for the purposes of the current Rose Institute analysis, the five-year data are the only data available by legislative district.

Congressional district data are available in one-year, three-year, and five-year ACS estimates, as are County estimates for counties over 60,000 in population. [State legislative districts are included only in the five-year data.] Comparing the 2009 one-year and 2005-2009 five-year estimates reveals the “collected over time” nature of the five-year estimates. The five-year data do not reflect the Bureau’s current population estimates for each jurisdiction (that will only come from the official 2010 decennial Census data, which will be available on or before March 31st, 2011). The differences among the data sets are clear when the 2009 one-year estimates are compared to the 2005-2009 five-year data. Since the five-year data are captured over time, the five-year estimates match the actual population in the district at some point in 2007 or 2008.

Projected and estimated population data predict the range the final census data are likely to fall within when available in late March of 2011. It is, however, a truism in demographics that “The one thing we are sure of is that all projections are wrong. But how wrong — and how right — is unknown.”

Excel Table for Download:

  • Download Excel table of ACS five-year and one-year estimates by County, CD, AD, and SD.

Interactive online maps:

In each map, to view the legend click on the button on the left side of the screen showing colored dots and lines (that resemble a legend).



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