Introduction to the U.S. Census of Population and Housing

Overview

• What is it and why do we care?
• How the data are collected
• What data are available?
• Introduction to Census geography and summary levels
• A Quick Look at the Census documentation
• A Quick Look at some sample data

What is it and Why Do We Care?

• The federal government must conduct a population census every 10 years as mandated by the Constitution of the United States
• The modern census of population and housing was established in 1940 with the incorporation of a new set of socio-demographic variables and the introduction of sampling techniques. In particular, the Census Bureau introduced for the Decennial Census Long Form (commonly refereed to as simply the Long Form) which included a much recorded a much expanded set of socio-demographic variables.
• Beginning in 2010, the Census Bureau replaced the Long Form with a different survey using a new sampling methodology , the American Community Survey (ACS). This change is arguably the most substantial change how the federal government captures and uses national socioeconomic data since the introduction of the Long Form in 1940
• Unlike the Long Form which provided point estimates of socio-demographic variables every 10 years, the ACS provides single and multi-year estimates of socio-demographic variables on a yearly basis. The level of geographic specificity of the estimate varies depending on the time span of the estimates (i.e. 5-year estimates have the highest level of geographic specificity while single year estimates have the lowest level of geographic specificity. Further, unlike the Decenial Census, the ACS is a is a representative sample of the US population and not a full count (also called a census)
• The ACS and the Decennial Census are the only sources for demographic data with a national geographic scope and the most reliable and detailed information for describing local areas, neighborhoods, cities, and counties
• These 2 surveys are also the most consistent source of national scope, time series, demographic data available
• Federal dollars for schools, employment services, highway assistance, housing construction, hospital services,programs for the elderly, etc. are all distributed based on the Decennial Census and ACS. Also, congressional representatives are apportioned based on census counts.

How the Data Are Collected

• Decennial Census data is collected from households through a mail survey and some outside interviews conducted every decade
• ACS data is also collected via a mail survey and some outside interview but it is collected on a continuous basis
• For the , 74 percent of US households responded to the mail survey. Data for about 22 percent of households that did not reply to the mail survey was collected via outside interviews
• The 2010 Census cost about $13 billion dollars. That's about $42 per capita. By way of comparison, the per capita cost of the 2010 Census by China was US$1 and for India it was US$0.40
• The Census Bureau distributes two different surveys to US households for the Decennial Census and the ACS:
  • The Decennial Census questionnaire contains questions asked of everyone
  • The ACS questionnaire contains questions asked of a population sample (1/14 households). The now discontinued Long Form, was also distributed to a sample of US households but the sampling rate was substantially higher than the ACS(1/6 households compared to 1/14 households)

• Decennial Census - Summary File 1 - 100% Count
  •  Population Characteristics                                                                   Housing Characteristics

    Total population	Number of housing units
    Race	Tenure(i.e. renter- or owner-occupied)
    Hispanic or Latino origin	Vacancy status
    Sex	Various cross-tabs with tenure
    Age	Occupancy status
    Marital status	Urban and rural
    Household size	Group Quarters
    Household relationships
    Household race and ethnicity
    Families

    • Sample Decennial Census Questionnaire
       
  •  ACS
    • Population
    Social Characteristics
    Education, Citizenship, Ancestry, Language, Disability, Children, Place of Birth, etc.
    • Economic Characteristics Income, Utility costs, labor force status, occupation, place of work, public assistance, vehicles available, etc.
    • Housing Age of housing, units in structure, facilities, telephone service, year moved into unit, fuel costs, etc.
    • Sample Long Form from 2000 Census
       
  • Why We Need to Know the Two Components
    • Accuracy of the data varies and counts differ (Why?)
    • It helps us to understand how the data are organized by the Census Bureau

  Census Geography and Summary Levels

  The Census organizes and aggregates data into a series of geographic hierarchies for for most of the data products it produces
  Overview
   

  Summary  Level	Geographic Unit
  010	United States
  020	Region - Northeast (NE), Midwest (MW), South (S) and West (W) Regions
  030	Division - NE -New England, Mid Atlantic; MW - East North Central, West North Central;                                      S - South Atlantic, East South Central, West South Central; W - Mountain, Pacific
  040	State - includes Washington D.C.
  050	County
  060	County Subdivision
  070	Place
  080	Census Tract / Block Numbering Area - average 4,000 persons
  090	Block Group - average 1,000 persons
  100	Block - average 85 persons

  
   
  State-County-Tract-Block Group Nesting
   

  Summary Level	Geographic Unit
  040	State - includes Washington D.C.
  050	County
  140	Census Tract
  150	Block Group

  • Supplemental geographic areas
   

  Summary Level	Geographic Unit
  400	Urbanized Areas
  300	Metropolitan Areas (MSAs, CMSAs)
  200	American Indian and Alaska Native areas
  800	ZIP codes

  A visualization of the Census Bureau's geographic hierarchy/summary levels
   

  • A Visual Look at Census Geography
  • Continental United States (Regions - blue; Divisions - green; States - brown)
  
   
  • Counties
  
   
  • A Closer Look at Southern New England Counties
    
    
    
  
   
  • Tracts and Block Groups in Suffolk County, Massachusetts (black lines; tracts in green)
    
    
    
  
   
  • Census Geography Concepts
    • The census block is the basic level
    • Confidentiality must be maintained, and data about individual persons and households are not revealed
    • More detailed data are provided for higher levels of geography (Why?)
    • Many, but not all, items are available at multiple summary levels
  • Potential Problems
    • The same geographic name is used for summary levels corresponding to different aggregations
    • Geographic areas at lower levels may be subdivided by higher levels of geographic units - e.g. split census tract
    • The same variable names are used for different variables in the two surveys>
    • Variable value encoding makes identifying the meaning of variable difficult
    • ZIP codes do not overlay other units cleanly
    • Geographic boundaries change with time, making time-series analysis difficult

  Decennial Census and ACS data is available online either by using American Factfinder, Social Explorer (MIT has a subscription to this service), or the Census Bureau's FTP server

  A Quick Look at the Census and ACS Documentation

  • 2010 Census Technical Documentation
  • ACS documentation
  • ACS "What Users Need to Know" Handbook. You probably want to take a look at the Handbook for General Data Users
  • State/County/Place FIPS Codes
  • Census Bureau Geographic Hierarchy/Summary Level Charts

  More Information about the 2010 Census and the ACS

  Response Rates for the ACS
  Census 2010 Release Dates
  Census 2010 Data Product Descriptions
  An Overview: Race and Hispanic Origin and the 2010 Census
  

  The section of these notes entitled "Introduction to the U.S. Census of Population and Housing" is adapted from a Microsoft PowerPoint presentation created by Qing Shen for a lecture he delivered to the MIT class 11.208 on January 21, 1997.

  Last modified by mailto:schulthe@mit.edu on 27 January 2015.