introduction to the american community survey north carolina state data center north carolina office...
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Introduction to theAmerican Community Survey
North Carolina State Data CenterNorth Carolina Office of State Budget & Management
Have You Read the News Lately?
There have been a lot of recent news items published referring to new Census numbers and something called the American Community Survey.
There are other stories, too.
We’ve Got Questions!
What’s happening with the Census? What are these new data? How do I use the data?
Decennial Census Data
Decennial Census runs every 10 years Basic demographic data to the census
block level is released through Summary Files 1 and 2
Detailed socio-economic data to at least the census tract level and in many cases to the census block group level is released through Summary Files 3 and 4
The Need for More Data
The socio-economic data on Summary File 3 is very useful, but …
The data is needed more often than once every 10 years.
Point-in-time data collection (i.e. April 1, Census Year) may not provide the most accurate picture of a community.
What is ACS?
Monthly, rolling survey to collect socio-economic data.
Annually reports data Data reported to the at least to the
census tract level. In many cases census block group data will be available
Replaces Summary Files 3 and 4!2010 Census will be short form only
Data Collection
Census 2000 Summary File 3 sent a long-form questionnaire to a 1 in 6 household sample nationally.
ACS sample will be smaller than the Census 2000 sample.
Decennial census surveys every 10 years
ACS surveys every month.
Rolling Monthly Survey
Sample addresses are selected every month from the MAF and surveys are mailed.
The following month, Computer Assisted Telephone Interviewing (CATI) will contact the non-responding households.
A month after CATI, Computer Assisted Personal Interviewing (CAPI) will contact the non-responding households.
Jan. Feb. March April May
Sample 1Mail
Sample 1CATI
Sample 1CAPI
Sample 2Mail
Sample 2CATI
Sample 2CAPI
Sample 3Mail
Sample 3CATI
Sample 3CAPI
Sample 4Mail
Sample 4CATI
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Sampling
Sampling will cover all census geographic levels.
Since the sample size is smaller, it will take more time to collect adequate data from smaller population areas.
This sample time requirement means that data will be reported differently for smaller population areas.
Data Reporting ACS data will be released annually. Data for areas with a population of
65,000 or more will be reported as single-year estimates.
Data for areas with a population between 20,000 and 64,999 will be reported as a 3-year average.
Data for areas with a population under 20,000 will be reported as a 5-year average.
Data Release Schedule
Type 2005 2006 2007 2008 2009 2010
Annual Est.
X* X X X X X
3-Year Avg.
X X X
5-Year Avg.
X
* - Data from test areas with a population of 250,000 or more
Data Available in 2006
2006 will be the first year of data for a fully-implemented ACS.
Earlier data is available for test sites, but these tests use slightly different methodologies.
Group quarters are not included in the test area data.
Test areas were generally based on areas with a population of 250,000 or more.
Data Releases in 2006 Demographic data was released in
mid-August. Economic data was released in late
August. Housing data will be released in
October. Special cross-tabulations will be
released in November. Data only for areas with a
population of 65,000 or more.
Data Products
Profilesdata, narrative, multi-year
Selected Population Profilesrace or ethnic group, ancestry
Tablessubject, detailed, custom
Ranking Tablesstates, counties, places
Mapsreference, thematic
Data Profiles
Demographic Sex and age, race, relationship, household by type
Social Education, marital status, veteran status, place of birth
Economic Income, employment, occupation, industry
Housing Occupancy and structure, housing value and costs, utilities
Narrative Profiles
Text based profile Select information from each of the
data profiles Bar charts of select data items Quick links to the Ranking Tables
main page
Selected Population Profile
Single profile combining demographic, social, economic and housing data items
Data is shown for a specified race/ethnic group including some multiple race and tribal groups or for a specified ancestry group
Tables
Detailed Multiple data items organized into a static table
Subject Data items from different detailed tables are organized into static, topic-related tables and organized under general subject headings
Custom User selects data items from desired detailed tables to create a unique data table
Ranking Tables
2005 ACS compares selected data item across all states.
Previous ACS data ranked counties and places.
Data items are organized by subject.
Sorts are dynamic and may be resorted by rank or alphabetically by geography name.
Geographic Comparison Tables
Shows select data as percentages or medians for all geographies within a state.
GCT tables list geographies alphabetically or numerically and, unlike ranking tables, are static.
There are approximately 65 GCT tables.
Geographic Comparison Table – 2005 Geographies
States Congressional Districts (109th Congress) Counties Places Public Use Microdata Areas School Districts Urban/Rural and Inside/Outside
Metropolitan and Micropolitan Statistical Areas
Maps
Reference maps show location of geographies with no data.
Thematic maps show selected data items, similar to those shown on the ranking tables, across user-selected geographies.
Thematic maps allow user to define data classes, boundaries, features, and titles.
FindingThe Numbers
Test area data reports an estimate, upper, and lower bounds.
2005 data reports an estimate and a margin of error.
ACS Data
All ACS data are estimates 90% confidence that the actual data
point is within the margin of error While this is a new way of presenting
the data, there has always been a confidence interval with Summary File 3 sample data.
ACS and Decennial Data
Since ACS and Summary File 3 are sample data products and ACS replaces the long form (Summary File 3), isn’t it OK to compare ACS data with decennial data?
NO!
ACS and Census – Comparison
Sample sizes are different Residency rules are different Legislative purposes are different Group Quarters data may be
missing Geographies may be different Users should not compare ACS
and SF3 data
ACS Table Names
Base table data is the most detailed and is the “base” for all other ACS tables and profiles
Census contains Population and Housing tables (i.e. P0010001, PCT159H001, H001001)
ACS contains Base and Collapsed tables (i.e. B03002, C03002, B05003H)
ACS Table Naming Structure
Initial letter identifies the type of table – base and collapsed
Following 2 digits identify subject area 01 – age and sex02 – race
There are 26 subject areas Next 3 digits are table sequence numbers An alphabetic suffix indicates race/ethnic
classifications and are not the same as the Census classifications
Collapsed Tables
Collapsed Table – Quick Guide
For some areas, the detailed Base Tables may have estimates that are unreliable.
Reliability, in the form of median coefficient of variation, is checked for all Base Tables for each area.
Coefficient of Variation = standard error/estimate If the median CV for a Base Table is less than 61%,
the table passes and is published. If the median CV for a Base Table is greater than
61%, the table fails.
Collapsed Table – Quick Guide
If a Base Table fails the check, some detailed estimates are “collapsed” into a single estimate in a Collapsed Table.
The median CV reliability check is now run on the Collapsed Table.
If the Collapsed Table passes the median CV check, it is published.
If the Collapsed Table fails the median CV check, it is dropped and not published.
Collapsed Tables – Last Word
The median Coefficient of Variation check is only done on Base Tables for single year data (i.e. for areas with a population of 65,000+) and for 3-year average data (i.e. for areas with a population from 20,000 to 64,499).
For 5-year average data, all Base Tables are published. There are no dropped or collapsed tables.
Standard disclosure rules apply to all ACS releases.
ACS and a ChangingWorld
ACS and Dynamic Geographies
Populations change Boundaries change ACS reports data as single year, 3-
year average, and 5-year average depending on the population of the area.
ACS accounts for these changes through sampling strategy and the Boundary and Annexation Survey.
Boundaries
Governmental unit boundaries are based on annual Boundary and Annexation Survey (BAS) benchmark file
Boundaries are as of January 1 of the reported year (i.e. 2005 ACS boundaries are as of January 1, 2005)
Non-governmental unit census geographies will be drawn once a decade prior to the decennial census
Sampling
Monthly samples include locations across census geographies.
Samples are collected each month for areas that are not in incorporated places.
When areas are annexed, their sampled data is added to the total for the annexing place.
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Sampling Controls
Households missed in the ACS survey can skew the data.
The US Census Bureau produces annual Intercensal Population Estimates for counties.
These estimates for total, age, race, sex, and Hispanic Origin populations and housing unit estimates are used as controls for ACS at the county level.
Sampling Controls The Intercensal Population Estimates are
NOT the same as the State Demographer’s estimates.
County level population, age, race, sex, Hispanic Origin, and total housing unit data on ACS will equal the Intercensal Population Estimates data (without Group Quarters data for 2005).
Underlying ACS survey data is not controlled and sums of data from Detailed Tables may not equal the controlled totals.
Using the American Community Survey
Points to Remember ACS and the Decennial Census are
separate products. Group quarters data are not included
in the 2005 ACS ACS data are estimates with margins
of error Single year data will be more volatile
than 3- or 5- year averages ACS is new and adjustments will
happen
Accessing ACS
American FactFinderhttp://factfinder.census.govclick “Data Sets”
North Carolina State Data Centerhttp://census.state.nc.us under “Survey Data from the US Census Bureau”
Questions
Bob [email protected] Carolina State Data CenterNorth Carolina Office of
State Budget & Management(919) 807-4781