American community survey
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American Community Survey. Susan Clapp Demographics & Workforce Group U.Va . Weldon Cooper Center for Public Service. What will I learn today?. ACS Basics ACS and the 2010 Census Accessing Data Using survey estimates What to watch out for Resources. What is the ACS?.

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American community survey

American Community Survey

Susan Clapp

Demographics & Workforce Group

U.Va. Weldon Cooper Center for Public Service


What will i learn today

What will I learn today?

  • ACS Basics

  • ACS and the 2010 Census

  • Accessing Data

  • Using survey estimates

  • What to watch out for

  • Resources


What is the acs

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.


American community survey 1353247

What is the ACS?

Population

Survey

Census


Where did the acs come from

Where did the ACS come from?

Continuous ACS replaced long form in 2005

  • The ACS has its roots in the Decennial Census long form.

Basics – age, gender, race, number of people

Details – income, education, language spoken, etc.

Short form Census every 10 years

Short form Census every 10 years

Short form and long form

Census every 10 years


How has the acs helped

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


What about the 2010 census

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

learn

How it should be used

To obtain

counts of the

To about the population’s

population and their basic

demographic, social, economic, and

characteristics

housing characteristics

Who is questioned

The entire population

A sample of the population

(over 130

million households)

(approximately 3 million households

each year)

Type of data

Counts

Estimates

with margins of error


What can we learn from the acs

What can we learn from the ACS?

Social Characteristics

Demographic Characteristics

Housing Characteristics

Economic Characteristics

learn

Financial Characteristics


Who takes the survey

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).

9


What do i need to know before i access the data

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


What are single and multi year estimates

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


Which estimates do i use

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…

    • 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


When are data released

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


Any questions

Any questions?


Access to data

Access to Data

  • American Factfinder

  • http://www.census.gov

    • Albemarle County

    • Greene County

    • Albemarle and Greene


Census vs survey

Census vs. Survey

Population

Survey

Census


Margins of error

Margins of Error

  • Surveys have error. The ACS tables give you the margin of error so you can use the estimates appropriately.


What do i do with the margins of error

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


Calculating confidence intervals

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.


American community survey 1353247

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!!


What do i do with the margins of error1

What do I do with the Margins of Error?

  • Take a look at them

  • Calculate the confidence interval

  • 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.


What else should i be aware of

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


What else should i be aware of1

2005

2006

2007

2008

2009

2010

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


What else should i be aware of2

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


Resources

Resources

  • www.census.gov/acs/www

  • http://www.census.gov/acs/www/Downloads/handbooks/ACSGeneralHandbook.pdf

  • http://www.coopercenter.org/demographics/


American community survey 1353247

Susan Clapp

(434)982-5690

[email protected]


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