Introduction to the American Community Survey

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Introduction to theAmerican Community Survey

• North Carolina State Data CenterNorth Carolina
  Office of State Budget Management

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Have You Read the News Lately?
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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.
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Weve Got Questions!

• Whats happening with the Census?
• What are these new data?
• How do I use the data?

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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

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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.

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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

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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.

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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.

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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.

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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.

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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
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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.

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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.

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Data Products

• Profiles data, narrative, multi-year
• Selected Population Profiles race or ethnic
  group, ancestry
• Tables subject, detailed, custom
• Ranking Tables states, counties, places
• Maps reference, thematic

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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
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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

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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

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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
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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.

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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.

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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

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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.

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FindingThe Numbers
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• Test area data reports an estimate, upper, and
  lower bounds.

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• 2005 data reports an estimate and a margin of
  error.

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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.

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ACS and Decennial Data

• Since ACS and Summary File 3 are sample data
  products and ACS replaces the long form (Summary
  File 3), isnt it OK to compare ACS data with
  decennial data?
• NO!

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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

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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)

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ACS Table Naming Structure

• Initial letter identifies the type of table
  base and collapsed
• Following 2 digits identify subject area 01
  age and sex 02 raceThere 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

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Collapsed Tables
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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.

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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.

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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.

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ACS and a ChangingWorld
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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.

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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

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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.

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Sampling Controls

• The Intercensal Population Estimates are NOT the
  same as the State Demographers 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.

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Using the American Community Survey
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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

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Accessing ACS

• American FactFinderhttp//factfinder.census.govc
  lick Data Sets
• North Carolina State Data Centerhttp//census.sta
  te.nc.us under Survey Data from the US Census
  Bureau

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Questions

• Bob Coats
• Bob.Coats_at_ncmail.net
• North Carolina State Data Center
• North Carolina Office of State Budget
  Management
• [phone]