Transcript American Community Survey

American Community Survey
Susan Clapp
Demographics & Workforce Group
U.Va. Weldon Cooper Center for Public Service
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What will I learn today?
• ACS Basics
• ACS and the 2010 Census
• Accessing Data
• Using survey estimates
• What to watch out for
• Resources
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What is the ACS?
• The American Community Survey (ACS) is an
ongoing survey that provides data every year -giving communities the current information they
need to plan and to provide services.
• Survey data help determine how more than $400
billion in federal and state funds are distributed each
year.
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What is the ACS?
Population
Survey
Census
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Where did the ACS come from?
• The ACS has its roots in the Decennial Census long form.
Basics – age, gender,
race, number of people
Short form
Census every
10 years
1910
Details – income, education,
language spoken, etc.
Short form and long form
Census every 10 years
1920 1930 1940 1950 1960
1970
Continuous ACS replaced
long form in 2005
Short form
Census every
10 years
1980 1990 2000 2010 2020 2030
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How has the ACS helped?
• Detailed data are available every year, not every 10
years
• ACS interviewers are professional, year-round
employees, not temporary employees hired every 10
years
• Faster, cheaper, and more accurate Decennial
Census
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What about the 2010 Census?
2010 Census
ACS
Purpose
To show the number of people To show how people in the U.S. live
who live in the U.S.
Length
10 questions
69 questions
Frequency
Once, April 1, 2010
Ongoing
How it should be used
To obtain counts of the
population and their basic
characteristics
To learn about the population’s
demographic, social, economic, and
housing characteristics
Who is questioned
The entire population
(over 130 million households)
A sample of the population
(approximately 3 million households
each year)
Type of data
Counts
Estimates with margins of error
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What can we learn from the ACS?
Demographic Characteristics
Age
Sex
Hispanic Origin
Race
Relationship to Householder
Economic Characteristics
Income
Food Stamps Benefit
Labor Force Status
Industry, Occupation, and Class of
Worker
Place of Work and Journey to Work
Work Status Last Year
Vehicles Available
Health Insurance Coverage
Social Characteristics
Housing Characteristics
Marital Status and Marital History
Year Structure Built
Fertility
Units in Structure
Grandparents as Caregivers
Year Moved into Unit
Ancestry
Rooms
Place of Birth, Citizenship, and Year Bedrooms
of Entry
Language Spoken at Home
Kitchen Facilities
Educational Attainment and School Plumbing Facilities
Enrollment
learn
Residence One Year Ago
House Heating Fuel
Veteran Status, Period of Military
Telephone Service Available
Service
Disability
Farm Residence
Financial Characteristics
Tenure (Owner/Renter)
Housing Value
Rent
Selected Monthly Owner Costs
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Who takes the survey?
• Resident population of the United States and
Puerto Rico – all people living in housing units
and group quarters
▫ A “group quarters” is a residence that is managed
by an organization providing housing or services
for residents (e.g. college dormitories, prisons,
and nursing homes).
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What do I need to know before I
access the data?
• Three different kinds of estimates
(data series)
▫ 5-year estimates for all
geographic areas
▫ 3-year estimates for areas with
20,000 or more
▫ 1-year estimates for areas with
65,000 or more
• Sample size (number of people
surveyed) is not large enough to
obtain annual estimates for small
geographic areas
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What are single- and multi-year
estimates?
• Data series are named for length of time required to
collect sufficient sample
▫ e.g. 1-year estimates are based on data collected over
a 1-year period
• 3- and 5- year estimates are known as multi-year
estimates because they are based on data collected
over multiple years
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Which estimates do I use?
• Use single-year estimates when…
▫ Currency (timeliness) is critical
▫ Researching large areas experience rapid change
▫ Examining year-to-year changes
• Use multi-year estimates when…
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Reliability of the data is critical
Analyzing data for small areas
Studying smaller populations in large areas
Examining a set of areas in which some areas have
only multi-year estimates
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When are data released?
• New estimates are released every year for all three
series
Year of Data Release
Data Series
2010
2011
2012
Years of Data Collection
1-year
2009
2010
2011
3-year
2007-2009
2008-2010
2009-2011
5-year
2005-2009
2006-2010
2007-2011
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What kinds of data exist?
• Profiles
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Data Profiles
Narrative Profiles
Comparison Profiles
Selected Population Profiles
• Tables
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Detailed Tables
Subject Tables
Ranking Tables
Geographic Comparison Tables
• Thematic Maps
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Any questions?
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Access to Data
• American Factfinder
• http://www.census.gov
▫ Albemarle County
▫ Greene County
▫ Albemarle and Greene
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Census vs. Survey
Population
Survey
Census
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Margins of Error
• Surveys have error. The ACS tables give you the
margin of error so you can use the estimates
appropriately.
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What do I do with the Margins of
Error?
• 1) Take a look at them
• 2) Calculate the confidence interval
▫ Confidence interval is a range – the Census Bureau is
90% confident that the true population statistic is
between A and B
A = Estimate – Margin of Error
B = Estimate + Margin of Error
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Calculating Confidence Intervals
A = 490-139 = 351
B = 490+139 = 629
The Census Bureau is 90%
confident that the true number
of Greene county residents, ages
60 to 64 years old, who own
their home, is between 351 and
629.
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Calculating Confidence Intervals
A = 50-57 = -7
B = 50+57 = 107
The Census Bureau is 90%
confident that the true number
of Greene county residents who
are Asian, 16+, working, and
commuting to work in their own
vehicle, is between -7 and 107.
Beware!!
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What do I do with the Margins of
Error?
1. Take a look at them
2. Calculate the confidence interval
3. When margins of error are too big, combine estimates
for small groups or small geographies – the
Demographics & Workforce Group can help with this!
• The most important step is #1. Always look at the
margins of error of an estimate before using that
estimate. If the margin of error is close to or bigger than
the estimate, you should take further steps.
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What else should I be aware of?
• Making comparisons
▫ Do not compare multi-year estimates to single-year
estimates
▫ When comparing two areas, only use data from the
same data series
▫ If comparing, for example, Albemarle County and
Greene County, use the data series they have in
common – ACS 5-year estimates
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What else should I be aware of?
• Assessing Change
▫ Do not assess year-to-year changes with multi-year
estimates
▫ Consecutive multi-year data contains data from
overlapping years
▫ The differences in overlapping estimates are driven by
the differences in the non-overlapping years.
ACS 2005-2009 5-year Estimates
ACS 2006-2010 5-year Estimates
2005
2006
2007
2008
2009
2010
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What else should I be aware of?
• New American Factfinder
▫ The Census Bureau is replacing their data access system with a new
website
▫ Right now, all ACS data are on the old system shown in the demo
• Timeline
▫ Late spring – Late summer 2011: ACS data will be phased into the new
system
▫ Fall 2011: Old Factfinder will be removed
• Links
▫ http://factfinder2.census.gov
▫ Tutorials: http://factfinder.census.gov/home/saff/aff2.html
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Resources
• www.census.gov/acs/www
• http://www.census.gov/acs/www/Downloads/handb
ooks/ACSGeneralHandbook.pdf
• http://www.coopercenter.org/demographics/
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Susan Clapp
(434)982-5690
[email protected]