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Census Background

Census Background. Census: 100 Percent Count of Units Survey: Sample of Units. Censuses. Decennial Census: Population and Housing Economic Census: Business and Industry Agriculture Census: Farms Census of Government: Local and State. U.S. Census Bureau Surveys http://www.census.gov/.

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Census Background

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  1. Census Background • Census: 100 Percent Count of Units • Survey: Sample of Units

  2. Censuses • Decennial Census: Population and Housing • Economic Census: Business and Industry • Agriculture Census: Farms • Census of Government: Local and State

  3. U.S. Census Bureau Surveyshttp://www.census.gov/ • Decennial Census Survey: Population and Housing • American Community Survey • Current Population Survey • Survey of Income Participation Programs • American Housing Survey

  4. International Program Center • Part of U.S. Census Bureau Population Division • Assist in Census data collection and processing for countries throughout the world • http://www.census.gov/ipc/www/

  5. Census of Population and Housing, 2000 (Short Form) • Seven Q’s • Name • Sex • Age • Relationship to Householder • Hispanic Origin • Race (can chose multiple categories) • Owner/Renter

  6. Census 2000 Survey (Long Form) • Includes all Q’s on Short Form • Densely populated sampling areas • (1 in 8 HHs surveyed) • Sampling areas less than 2,500 persons • (1 in 2 HHs surveyed) • In US as a whole • (1 in 6 HHs surveyed)

  7. Ancestry Migration Physical Disability Income Marital Status Occupation Journey to Work Place of Birth Education Language Veteran Status Labor Force Status Census 2000 Survey Topics for Persons

  8. Census 2000 Survey Topics for Families • Grandparents as caregivers • Poverty

  9. Vacancy Status Units in Structure Number of Rooms Number of Bedrooms Farm Residence House Value Monthly Rent Housing Costs Year Moved into Residence Plumbing and Kitchen Facilities Heating Fuel Telephone Service Vehicles Available Census 2000 Survey Topics for Household Units

  10. ACS Concepts, Definitions, Overview

  11. What is the ACS? • A large, continuous demographic survey • Produces annual and multi-year estimates of characteristics of population and housing • Produces information for small areas including tracts and block groups and is updated every year • Key component of the reengineered 2010 Census of Population and Housing

  12. ACS Background • Leslie Kish’s idea for a “rolling census”, Roger Herriot’s suggestion for decadal census program with continuous survey, Chip Alexander and others efforts for Continuous Measurement Survey • Context of early 1990s: simplify decennial census, reduce census costs, provide more timely data

  13. ACS Sample Design • Contact about 3 million households each year, about 250,000 per month, in every U.S. county • Survey includes households in all 50 states, District of Columbia, and Puerto Rico and will include both housing units and group quarters

  14. Sampling Rates

  15. Sample Design • Accumulate sample over time to produce lowest levels of geographic detail • Annual estimates for population size of 65,000+ • Three-year averages for 20,000+ • Five-year averages for census tracts and block groups

  16. ACS Implementation Schedule • ACS testing and development: 1996-2004 • ACS full implementation: Jan 2005 • First full implementation data products: Summer, 2006

  17. Data Availability Schedule

  18. Two Major Forms of ACS Data 1. Summary Files/Tabulations 2. Microdata samples of individual household records (PUMS)

  19. Summary Files/Tabulations • These are tables that report summary of cases for different categories --# persons by age and sex for a census tract --% of families with grandparent caregiver in a county • Not all possible combinations of variables can be tabulated, so only ones of major interest are tabulated

  20. Advantages of Summary Tabulations • The major advantage is that they present a standardized tabulation for similar geographic units • For example, one can obtain the proportion of Black households in poverty of all census tracts in a metropolitan area

  21. Limitation of Summary Tabulations • Summary tabulations are presented in a fixed format with limited flexibility for the analysts to make adjustments • Analysts can collapse categories but there is not ability to obtain more detailed categories or to add additional variables

  22. U.S. Census Geography

  23. Geographic Concepts • Census geography is important for locating data but also because of the organization of the geographic hierarchy • Census geography is structured in a generally hierarchical fashion, ranging from larger to smaller units, with smaller units contained within the boundaries of larger units

  24. Geographic Hierarchy • United States (n=1) • Region (n=4) • Division (n=9) • State, including D.C. (n=51) • County (or equivalent, n=3,141) • Place (n~39,000) (not in strict hierarchy) • Census tract • Block group • Block (n~7,000,000) • Housing unit

  25. Supplemental Geographic Units • Urbanized area and urban/rural areas • Metropolitan areas (MSA and CMSA) • American Indian and Alaska Native areas • Congressional districts • ZIP code areas • Traffic Analysis Zone (TAZ) areas • School districts • User-Defined Area Programs (UDAP)

  26. Hierarchy of Data Availability • Corresponding to the hierarchy of geographic units is a hierarchy of the detail of census data • More detail (more variables and more categories in variables) are available for larger geographic units • Census tract data has more detailed data than blocks or block groups

  27. Data Access • The U.S. Census Bureau website offers access online to ACS profiles and tables http://www.census.gov/acs/www/ • Users can request special tabulations for ACS data • There are several Secure Census Research Centers that may offer specialized data access

  28. Microdata (PUMS) • The second main ACS data type closely resembles the actual data collected in the ACS survey questionnaire • All person identifiers are removed and the microdata have limited geographic identifiers

  29. PUMS • PUMS data include original survey variables and some derived measures • Includes records for housing unit and for each person in occupied housing units

  30. Uses of PUMS • Microdata is a flexible form of survey data • Offers more specialized combinations of data that researchers can craft for special purposes • Downside is that geographic areas are fairly large

  31. ACS Sampling Frame • Select households from Master Address File (MAF) updated from 2000 census • Continuously update MAF through use of (a) delivery sequence files from USPS and (b) updated addresses through the U.S. Census Bureau’s community address updating system

  32. ACS Data Collection Process • Obtain overlapping monthly samples using three data collection systems • Mail: make initial attempt at collection by mail questionnaire • Phone: telephone follow-up of incomplete mail returns from 3 CATI facilities • Personal visit: subsample incomplete returns by CAPI using laptops

  33. Data Collection Process: Response Rates by Mode and Nativity

  34. English Proficiency and Response Rates, Houston

  35. Comments about Foreign-Born • Current mail questionnaire in English only, with Spanish upon request • Phone and in-person visit available in English and Spanish • But: language barriers are problem • Currently, informal methods are used to complete the interviews • Need improved methods for other languages

  36. Lowest Rates for: Sex Citizenship Phone availability Grandchildren at home Monthly condo fee Highest rates for: Mobile home costs Property insurance Other mortgage Real estate taxes Year house built ACS Item Nonresponse, 2003

  37. Sample Weights • Initial weights reflect the probability of selection • Weights are adjusted for interviewed households to account for noninterviews • Weights are adjusted to independent housing unit and population estimates (i.e. population controls)

  38. Population Control Totals • Intercensal population estimates are produced by updating previous decennial census results with administrative records • Control totals for housing units and population (by age, sex, and race/ethnicity) are made annually for counties (or group of counties) • Housing unit and population adjustment factors are applied to sample weights to derive housing and population weights consistent with population control totals

  39. Some Key Reminders • Annual data for small areas will be moving five-year averages • Annual data for all areas involve a “margin of error” due to sampling

  40. Differences from Traditional Census • 1. Data Content • The ACS survey questionnaire includes basically the same set of data content as the survey questionnaire (the “long form”) for the decennial census 2000

  41. Differences from Traditional Census Survey • 2. Variable Definitions • Many of traditional census survey questions are asked in a slightly different form • Census and earlier ACS include a racial category for “Black, African American, or Negro” • ACS for 2003 and after includes a category for “Black or African American”

  42. Differences from Traditional Census • 3. Temporal Aggregation • ACS: for larger (65,000+) population units, data will be available annually, albeit collected throughout the year • For smaller geographic units, data will be aggregated over time, for moving 3-year and 5-year averages

  43. Differences from Traditional Census • 4. Residence Rules • ACS collected data using a current residence rule, a “two-month rule” that defines a resident who has been in the same place for at least two months • Unlike the decennial census that uses usual residence rule, collecting April 1st data on the characteristics of usual residents

  44. Differences from Traditional Census • 5. Reference Period • The traditional census used April 1 as reference for time related variables • Age • residence 5-years prior • Because of the rolling nature of the ACS, the reference date is always shifting

  45. Differences from Traditional Census • 6. The Migration Question • The traditional census survey asked about residence 5-years prior to the April 1 • ACS asked about residence 5-years prior in 1996-1998 • ACS shifted to residence 1-year prior in 1999

  46. Multi-Year Statistics • Most multi-year statistics are calculated by combining the ACS data for each year • Estimates are computed using the geographic boundaries for the most recent year of the period • Dollar valued data items are adjusted for inflation to the most recent year in the period

  47. Example of Multi-Year Statistics • Percent foreign-born for year 1: Number Foreign-Born N1 ------------------------------------------ = ----- Total Population T1

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