Moving from the Census to Moving from the Census to the American Community the American Community

SurveySurvey

Richard LycanRichard LycanPopulation Research CenterPopulation Research Center

Portland State UniversityPortland State University

North American North American Cartographic Information SocietyCartographic Information Society

October, 2008October, 2008

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PRC – Who we arePRC – Who we are► An applied research center:An applied research center:

College of Urban and Public AffairsCollege of Urban and Public Affairs Portland State UniversityPortland State University

► The Oregon link with the U.S. Census Bureau for:The Oregon link with the U.S. Census Bureau for: Population EstimatesPopulation Estimates Census State Data CenterCensus State Data Center

► Courses in applied demographyCourses in applied demography

► Contract demographic researchContract demographic research

► Staffing a mix of demographers, geographers, and plannersStaffing a mix of demographers, geographers, and planners

► George Hough, PRC Director, usually with me to answer the tough George Hough, PRC Director, usually with me to answer the tough questionsquestions

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Outline for PresentationOutline for Presentation

► Some background and history on the Census Some background and history on the Census of Population and Housing and the American of Population and Housing and the American Community Survey (ACS) Community Survey (ACS)

► What demographers and other scholars are What demographers and other scholars are saying about the pros and cons of the ACSsaying about the pros and cons of the ACS

► Examples showing use of data from the ACSExamples showing use of data from the ACS

► Sources for more informationSources for more information

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Part 1 – Part 1 – Introduction to the Census Introduction to the Census

and the ACSand the ACS

► There will be no 2010 Census There will be no 2010 Census long form long form datadata on income, poverty, housing values, on income, poverty, housing values, and dozens of other socio-economic and dozens of other socio-economic characteristics of persons, households, characteristics of persons, households, and housing unitsand housing units

► Instead, these data are becoming Instead, these data are becoming available from the available from the American Community American Community Survey (ACS)Survey (ACS) on an annual basis on an annual basis

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A Very Short History of the Census A Very Short History of the Census ► 17871787 - - Article 1, Section 2 of the U.S. Constitution requires that a census of the Article 1, Section 2 of the U.S. Constitution requires that a census of the

population be conducted every ten years so that the representatives in Congress and population be conducted every ten years so that the representatives in Congress and direct taxes might be apportioned. direct taxes might be apportioned.

► 17901790 - - Federal marshals conduct the first census by going door-to-door through the 13 Federal marshals conduct the first census by going door-to-door through the 13 states plus the districts of Maine, Vermont, Kentucky, and the Southwest Territory states plus the districts of Maine, Vermont, Kentucky, and the Southwest Territory (Tennessee). (Tennessee).

► 19401940 - - Statistical sampling techniques are introduced, which allow the Census Bureau to Statistical sampling techniques are introduced, which allow the Census Bureau to create a “long form” answered by only a subset of the population, the source for topics create a “long form” answered by only a subset of the population, the source for topics such as income and poverty. such as income and poverty.

► Mail surveys, computers, the internet, wars, Elvis, TIGERMail surveys, computers, the internet, wars, Elvis, TIGER

► 1990’s1990’s – Initial planning for “continuous measurement” approach used in ACS – Initial planning for “continuous measurement” approach used in ACS

► 20002000 - - Last use of the “long form” in the Decennial Census. To be replaced by the Last use of the “long form” in the Decennial Census. To be replaced by the annual American Community Survey (ACS)annual American Community Survey (ACS)

► 20062006 - - Initial public release of the ACS data. Initial public release of the ACS data.

► 20102010 – Release of the ACS data for all geographies down to block group level – Release of the ACS data for all geographies down to block group level

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An Oversimplified View of the 2000 An Oversimplified View of the 2000 CensusCensus

► Build master address file (MAF) of all residential addresses in USBuild master address file (MAF) of all residential addresses in US

► Refine and finalize the questionnaireRefine and finalize the questionnaire

► Build the maps and geography filesBuild the maps and geography files

► Test the census – survey, tabulate, evaluateTest the census – survey, tabulate, evaluate

► Hire thousands of temporary workersHire thousands of temporary workers

► Collect the data: mail-out, field follow-upCollect the data: mail-out, field follow-up

► Tabulate the results: make many adjustments, create summary Tabulate the results: make many adjustments, create summary tablestables

► Publish the results: print, CD, InternetPublish the results: print, CD, Internet

► Get ready for the 2010 CensusGet ready for the 2010 Census

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The Paired SurveysThe Paired Surveys

► Since 1940 there have been two key components to the Since 1940 there have been two key components to the Decennial Census Decennial Census

The The “short form”“short form” survey is comprised of approximately 7 survey is comprised of approximately 7 items asked of every household, the results sometimes items asked of every household, the results sometimes known as known as Summary File 1Summary File 1

The The “long form” “long form” survey comprised of approximately 40 survey comprised of approximately 40 items asked of about 1 in 6 households, the results items asked of about 1 in 6 households, the results sometimes known as sometimes known as Summary File 3Summary File 3

The two components are linked in that data from the The two components are linked in that data from the “short form” are used to adjust results from the “long “short form” are used to adjust results from the “long form” by age, race, housing units, etc.form” by age, race, housing units, etc.

No “long form” in No “long form” in 20102010

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How the ACS Collects DataHow the ACS Collects Data► Surveys approximately 250,000 households each Surveys approximately 250,000 households each

monthmonth

► Uses professional survey staff rather than temporary Uses professional survey staff rather than temporary hires as in the Decennial Censushires as in the Decennial Census

► Uses a Master Address File to attempt to identify all Uses a Master Address File to attempt to identify all households in the US. Also gathers data from group households in the US. Also gathers data from group quarters residentsquarters residents

► Uses a mail-out census form with follow-up telephone Uses a mail-out census form with follow-up telephone and field interviewsand field interviews

► The survey contains 55 questions for persons and 30 The survey contains 55 questions for persons and 30 for housing units, about same as long form 2000 for housing units, about same as long form 2000 censuscensus

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Tabulation and Publication of the Tabulation and Publication of the ACSACS

► Similar to the 2000 CensusSimilar to the 2000 Census Tables are similar to those for the sample data (SF3) in the Tables are similar to those for the sample data (SF3) in the

2000 Census2000 Census Geographies are similar to those in the 2000 Census data – Geographies are similar to those in the 2000 Census data –

states, counties, cities, tracts, school districts, zip code states, counties, cities, tracts, school districts, zip code areas, and many others, but no block level data. There will areas, and many others, but no block level data. There will be Public Use Micro-sample (PUMS) databe Public Use Micro-sample (PUMS) data

► Differs from the 2000 CensusDiffers from the 2000 Census Data will become available sooner after collectionData will become available sooner after collection Data will be available on an annual basisData will be available on an annual basis Some data will be available for a single year but much will Some data will be available for a single year but much will

only be published for 3 and 5 year averagesonly be published for 3 and 5 year averages There will be no paired “short form” data to use to adjust There will be no paired “short form” data to use to adjust

the ACS survey resultsthe ACS survey results

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Geographies for the ACSGeographies for the ACS

► The geographies for the ACS are basically the same as for the 2000 CensusThe geographies for the ACS are basically the same as for the 2000 Census

The hierarchy of states-counties-tracts-block groupsThe hierarchy of states-counties-tracts-block groups

Metro areas, cities, census designated placesMetro areas, cities, census designated places

Other geographies – congressional districts, zip code areas, school Other geographies – congressional districts, zip code areas, school districts, TAZ’s, rural areas of 60,000+ populationdistricts, TAZ’s, rural areas of 60,000+ population

► Some boundaries change: political jurisdictions annually, school districts every Some boundaries change: political jurisdictions annually, school districts every two yearstwo years

► Block groups generally the smallest geography available, no block level dataBlock groups generally the smallest geography available, no block level data

► Reference maps in PDF format and boundary files in SHP format on Reference maps in PDF format and boundary files in SHP format on WWW.CENSUS.GOVWWW.CENSUS.GOV

..

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The Release ScheduleThe Release Schedule

► One year, three year, and five year dataOne year, three year, and five year data

► Data now available for larger areas such as Data now available for larger areas such as counties, larger school districts, PUMS areascounties, larger school districts, PUMS areas

► Issues of statistical reliability and Issues of statistical reliability and confidentiality limit detailconfidentiality limit detail

► Multi-year Multi-year data data a solution a solution

Year of releaseType of data 2006 2007 2008 2009 2010 2011 2012

Single Year Estimates 65,000+

3 Year Estimates 20,000+

5 Year Estimates

Population Size and Area

Census tracts and Block Groups

Averaging for five year data

2005 2006 2007 2008 2009 20102010 Release X

2011 Release X

Averaging for three year data

2005 2006 2007 20082008 Release X

2009 Release X

Note that only the beginning and end years differ in the data

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For Example: ACS Data For Oregon School For Example: ACS Data For Oregon School DistrictsDistricts

► Now – Single Now – Single year data only year data only available for available for districts districts 65,000 and 65,000 and over over

► Nov. 2008 – Nov. 2008 – three year data three year data for districts for districts 20,000 and 20,000 and overover

► Late 2010 – Late 2010 – five year data five year data for all districts, for all districts, plus 3 year and plus 3 year and 1 year data1 year data

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Part 2 – Part 2 – What Demographers and Others What Demographers and Others

Are Saying about the ACSAre Saying about the ACS

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Pay Attention to Pay Attention to Sampling ErrorsSampling Errors

► ACS sample smaller:ACS sample smaller: For five year data the For five year data the ACS sample is smaller than that for the ACS sample is smaller than that for the Census long formCensus long form

► We have sinned:We have sinned: Sampling errors a Sampling errors a problem with previous census data, but we problem with previous census data, but we tended to ignore, especially in mapping of tended to ignore, especially in mapping of the datathe data

► You can’t ignore it:You can’t ignore it: The ACS provides The ACS provides explicit data on confidence limits whereas explicit data on confidence limits whereas the 2000 census provided calculating the 2000 census provided calculating formulasformulas

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Data Will Be Better for Large Areas, Data Will Be Better for Large Areas, Poorer For Small AreasPoorer For Small Areas

► Annual data:Annual data: At the state, county, large school At the state, county, large school district level publication of annual data will allow district level publication of annual data will allow tracking of changestracking of changes

► Better surveys:Better surveys: The use of professional surveyors The use of professional surveyors and careful use of telephone and field follow-ups and careful use of telephone and field follow-ups will result in more complete questionnaires and less will result in more complete questionnaires and less “imputation”“imputation” for missing entries for missing entries

► Larger sampling errors:Larger sampling errors: For small areas such as For small areas such as census tracts data will only be available as five year census tracts data will only be available as five year averages. Sampling errors may be largeaverages. Sampling errors may be large

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Weighting of the SampleWeighting of the Sample

► Need to inflate sample:Need to inflate sample: If you sample 1 in If you sample 1 in 10 households, the results need to be 10 households, the results need to be inflated by a factor of roughly 10 (more inflated by a factor of roughly 10 (more complicated than this)complicated than this)

► The long and the short of it:The long and the short of it: The Census The Census long form data could be weighted from the long form data could be weighted from the short form data by households, population, short form data by households, population, race , age, sexrace , age, sex

► Weighting weaker for ACS:Weighting weaker for ACS: The ACS data The ACS data will be weighted from various Census will be weighted from various Census Bureau estimatesBureau estimates

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Some Suggestions on Using ACS Some Suggestions on Using ACS Data – Linda GageData – Linda Gage

► Don’t try to analyze all of the data at once, even if Don’t try to analyze all of the data at once, even if you use all of the items.you use all of the items.

► Concentrate on the data items that you already use Concentrate on the data items that you already use in your work.in your work.

► Don’t assume the Census data are more accurate Don’t assume the Census data are more accurate than ACS.than ACS.

► Compare Census and ACS data to administrative Compare Census and ACS data to administrative records that you have available.records that you have available.

► Consider whether the data make sense.Consider whether the data make sense.► Learn to use and provide the standard errors Learn to use and provide the standard errors

provided with the ACS.provided with the ACS.► Share what you learn about using the ACS with the Share what you learn about using the ACS with the

Census Bureau and other professionals.Census Bureau and other professionals.

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Part 3 – Part 3 – Examples Using the ACSExamples Using the ACS

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Example 1 – Viewing Tabular Data Example 1 – Viewing Tabular Data from the 2005 ACSfrom the 2005 ACS

► The next data are for The next data are for Public Use Micro-Public Use Micro-Sample Areas Sample Areas (PUMAs) and school (PUMAs) and school districts with districts with populations 65,000 populations 65,000 and greaterand greater

► PUMA’s have more PUMA’s have more than 65,000 persons than 65,000 persons and single year data and single year data are available for all of are available for all of them.them.

► However, sampling However, sampling errors can be large.errors can be large.

Data for sub-county areas

Several counties combined toReach 100,000 threshold

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Data for Oregon School DistrictsData for Oregon School Districts► The “margin of error” is for the 90% confidence level. This is The “margin of error” is for the 90% confidence level. This is

the type of error reporting used in the ACS. These data are for the type of error reporting used in the ACS. These data are for a PUMA, many of which have over 100,000 populationa PUMA, many of which have over 100,000 population

► Note the range for kindergarten enrollment of 1,046 – 2,068Note the range for kindergarten enrollment of 1,046 – 2,068

Selected Social CharacteristicsPUMA 00100, Oregon Estimate Margin of Error Lower Bound Upper BoundPopulation 3 years and over enrolled in school 27,935 +/-1,271 26,664 29,206Nursery school, preschool 1,510 +/-468 1,042 1,978Kindergarten 1,557 +/-511 1,046 2,068Elementary school (grades 1-8) 13,179 +/-852 12,327 14,031High school (grades 9-12) 6,900 +/-745 6,155 7,645College or graduate school 4,789 +/-1,033 3,756 5,822

EDUCATIONAL ATTAINMENTPopulation 25 years and over 75,473 +/-1,139 74,334 76,612Less than 9th grade 5,263 +/-717 4,546 5,9809th to 12th grade, no diploma 6,974 +/-982 5,992 7,956

High school graduate (includes equivalency) 25,060 +/-2,142 22,918 27,202Some college, no degree 19,635 +/-1,657 17,978 21,292Associate's degree 4,920 +/-926 3,994 5,846Bachelor's degree 9,021 +/-1,185 7,836 10,206Graduate or professional degree 4,600 +/-803 3,797 5,403

Percent high school graduate or higher 83.8 +/-1.5 82.3 85.3Percent bachelor's degree or higher 18 +/-1.8 16.2 19.8

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Or, consider the variability in enrollment Or, consider the variability in enrollment data for school districtsdata for school districts

► The values in red show estimates that have a margin of error The values in red show estimates that have a margin of error at least 20% of the estimate, then at least 10%at least 20% of the estimate, then at least 10%

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Example 2 - Analysis of change Example 2 - Analysis of change using census tract level datausing census tract level data

► Housing tenureHousing tenure – Large universe, modest – Large universe, modest change from year to year. We examine the change from year to year. We examine the change from 2001 to 2003 using ACS five change from 2001 to 2003 using ACS five year data for 1999-2003 and 2001-2005. year data for 1999-2003 and 2001-2005.

► CitizenshipCitizenship – Small universe (foreign born) – Small universe (foreign born) and modest change from year to year. We and modest change from year to year. We use the same data as above.use the same data as above.

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Housing Tenure Change - Census Housing Tenure Change - Census TractsTracts

1999 2000 2001 2002 20032001 2002 2003 2004 2005

► A large universe. A large universe. Overlapping time Overlapping time periods.periods.

► % in 2001% in 2001► % in 2003% in 2003► Varies from Varies from

county meancounty mean

► % Change% Change► @ 60% @ 60%

significancesignificance► @ 80% @ 80%

significancesignificance► @ 90% @ 90%

significancesignificance► @ 95% @ 95%

significancesignificance

Tracts with values significantly different than the county average of 42.7%

There remain a number of tracts for which change over time is statistically significant and they appear not to be random in space.

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Housing Tenure – Grid Map GeneralizationHousing Tenure – Grid Map Generalization

► Choropleth Choropleth mappingmapping

► Allocation to Allocation to census block census block centroidscentroids

► Grid map Grid map generalizationgeneralization 0.25 sq mi0.25 sq mi 0.50 sq mi0.50 sq mi 1.00 sq mi1.00 sq mi 1.50 sq mi1.50 sq mi

The highly generalized form of the contours may lend itself to easier verbalization of the spatial patterns.

How would one assess statistical significance?

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1999 2000 2001 2002 2003 2004 20051999 2000 2001 2002 2003 2004 2005

Change in Foreign Born Who Are Citizens – Change in Foreign Born Who Are Citizens – Census TractsCensus Tracts

► A smaller universe A smaller universe than for housing. than for housing. Overlapping time Overlapping time periods.periods.

► % in 2001% in 2001► % in 2003% in 2003► Varies from county Varies from county

mean?mean?

► % Change% Change► @ 60% significance@ 60% significance► @ 80% significance@ 80% significance► @ 90% significance@ 90% significance► @ 95% significance@ 95% significance

Significantly different from

county percent of 37.4

who are citizens

This doesn’t look good!

Only a few tracts show change that is statistically significant, fewer than one would expect by chance. I would not publish this map.

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Example 3 – The Published Tables Are But One Example 3 – The Published Tables Are But One Representation of RealityRepresentation of Reality

► The following example shows the large sampling variability in The following example shows the large sampling variability in the block group data using the block group data using % rental households of all single % rental households of all single family householdsfamily households..

► The universe of households was recreated from the 100% The universe of households was recreated from the 100% data from the 1990. data from the 1990.

► 20 random samples were drawn on a 1 in 6 basis.20 random samples were drawn on a 1 in 6 basis.

► Choropleth maps were draw for each sample?Choropleth maps were draw for each sample?

► Which map is the right one, the best representation of reality?Which map is the right one, the best representation of reality?

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Here are 20 “might have been” samples Here are 20 “might have been” samples for 1990 SF3 sample datafor 1990 SF3 sample data

► The following The following sequence shows 20 sequence shows 20 possible sets of data possible sets of data that might have that might have been obtained in the been obtained in the sampling process.sampling process.

► Note the Note the considerable local considerable local variation but also variation but also the persistence of the persistence of some of the high some of the high valuesvalues

► The lesson: The lesson: Be Be cautious about cautious about interpreting small interpreting small area sample census area sample census data.data.

Which of these 20 representations of reality is closest to the truth?

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► On running 100’s of On running 100’s of sampling simulations sampling simulations for row houses and for row houses and condos we think we condos we think we came up with an came up with an image of image of ElvisElvis

► Can you see an Can you see an image of Elvis in this image of Elvis in this map?map?

► Beware:Beware: you can get you can get some strange some strange geographical geographical coincidences in maps coincidences in maps of sample dataof sample data

No telling what you can find No telling what you can find in some weird samplein some weird sample

??

??

??

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Suggestions on mapping with ACS Suggestions on mapping with ACS datadata

► ReliabilityReliability - Inform your readers that the map is based on - Inform your readers that the map is based on sample data and the reality might vary. Where you can, provide sample data and the reality might vary. Where you can, provide quantitative measures of error. quantitative measures of error.

► Period averages -Period averages - Inform your readers when the data are for a 3 Inform your readers when the data are for a 3 or 5 year period, and what this means in the particular context.or 5 year period, and what this means in the particular context.

► Aggregate, Aggregate - Aggregate, Aggregate - Reduce standard errors by aggregating Reduce standard errors by aggregating over longer time periods or for larger geographies. Avoid over longer time periods or for larger geographies. Avoid mapping with block group level data.mapping with block group level data.

► Broaden class intervals -Broaden class intervals - Look at the standard errors in the data Look at the standard errors in the data when setting class intervals so as not to give a false impression when setting class intervals so as not to give a false impression of precision.of precision.

► Educate your clients - Educate your clients - Let them know the limits of the ACS data Let them know the limits of the ACS data for mapping. Say “no” to ill conceived requests.for mapping. Say “no” to ill conceived requests.

► Share -Share - Share what you learn about mapping with the ACS with Share what you learn about mapping with the ACS with colleagues. Provide feedback to the Census Bureau.colleagues. Provide feedback to the Census Bureau.

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Where does one get the ACS data?Where does one get the ACS data?

► ACSACS: http://www.census.gov/acs/www/: http://www.census.gov/acs/www/

► American Factfinder:American Factfinder:

► FTP Site:FTP Site: http://www2.census.gov/acs/MultiYearEstimates/http://www2.census.gov/acs/MultiYearEstimates/

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Additional ResourcesAdditional Resources► US Census Bureau ACS: US Census Bureau ACS: http://www.census.gov/acs/wwwhttp://www.census.gov/acs/www//

► Population Reference Bureau: The American Community Survey, Population Reference Bureau: The American Community Survey, http://www.prb.org/pdf05/60.3The_American_Community.pdfhttp://www.prb.org/pdf05/60.3The_American_Community.pdf

► National Academy of Sciences: Using the American Community National Academy of Sciences: Using the American Community Survey: Benefits and Challenges, forthcoming in paperback, Survey: Benefits and Challenges, forthcoming in paperback, http://books.nap.edu/catalog.php?record_id=11901http://books.nap.edu/catalog.php?record_id=11901

► Population Research and Policy Review (2006), No 25: A Special Issue Population Research and Policy Review (2006), No 25: A Special Issue on the ACS: on the ACS: http://www.springerlink.com/content/102983http://www.springerlink.com/content/102983//

► Missouri Census Data Center: Ten Things to Know about The ACS: Missouri Census Data Center: Ten Things to Know about The ACS: http://mcdc2.missouri.edu/pub/data/acs2005/Ten_things_to_know.shthttp://mcdc2.missouri.edu/pub/data/acs2005/Ten_things_to_know.shtmlml

► Portland Demographic Trends CDPortland Demographic Trends CD – Copies available, see – Copies available, see presenter.presenter.

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The EndThe End

Richard LycanRichard LycanPopulation Research CenterPopulation Research CenterPortland State UniversityPortland State UniversityPortland, Oregon, 97207-0751Portland, Oregon, 97207-0751

lycand@pdx.edu