Making Sense of the CensusSeptember 29, 201011.520: A Workshop on Geographic Information Systems11.188: Urban Planning and Social Science LaboratoryCensus Discussion Overview Utilizing Large Tabular Datasets (US Census)  Understand key aspects of US Census Data  What is it and why do we care? How are the data 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 Understand nature and use of large, highly structured, public datasets  Examine primary US Census Data (SF3=Summary File 3) at the block group level  Appreciate differences between Census SF3 CDs and third-party census extracts  Learn how to manipulate census data in MS-Access and ArcGIS2 Isn't this easy? We did thematic map of income on day 1!  Yes, if desired variable is already in attribute table of map There are thousands of variable in the 'long form' census  Which combinations zero in on useful indicator Drilling down and combining data are often needed  What do we mean by 'income'  Household, personal?? Earned income, all income??  At what scale? state, county, city, tract, block group?? For what time period? weekly, yearly, part-time?? 3Example - Thematic map of Income (viz., median earnings) Example: median 1999 personal earnings from the 2000 US Census  Variable P85 (among the hundreds of census variables and thousands of columns)  P85 records "Median earnings in 1999 dollars by sex for the population 16 years and over with earnings"  'earnings' includes wages, salaries, and net self-employment income (but not entitlements) The P85 table has three columns:  P085001 = total (for universe of population 16+ years old with earnings) P085002 = male P085003 = female4Example - Thematic map of Income (viz., median earnings) Use MS-Access database in class locker: M:\data\census2k\hw2_sf3_lite.mdb Two of the 70+ raw US census files (for Massachusetts) have already been loaded  Determine the median earnings for Cambridge block groups  Understand census data structure and use of raw data  Examine ER diagram of relationships among the tables used in this query Illustrate SQL query development in MS-Access  Save query and 'make table' to have results available in both forms 5Example - Thematic map of Income (viz., median earnings)Example - Thematic map of Income (viz., median earnings)  Map median earnings for Cambridge block groups  Bring MS-Access query results into ArcMap  Create thematic map  Examine Technical Documentation for the SF3 Census data  Online site at US Census: http://www.census.gov/prod/cen2000/doc/sf3.pdf Copy in class locker (for faster access): http://mit.edu/11.520/data/census2k/sf3.pdf Learn how to identify variables of interest and find them in the data tables 6Examples: Research Projects based on Census7 Sources: http://livingwage.mit.edu/; http://povertyinamerica.mit.edu/What Is the Census Mandated by the Constitution of the United States Census History The first census took place in 1790 to determine the number of seats each state would have in the U.S. House of Representatives.  The census was created to gain a better understanding of where people lived and to establish patterns of settlement as the nation grew. The modern census of population and housing was established in 1940 with the incorporation of the housing component and the introduction of sampling techniques for the long form Census Bureau The Census Bureau was established in 1902.  Today, in addition to administering the census of population and housing, the Census Bureau conducts more than 200 annual surveys, including the American Community Survey, the Current Population Survey and economic censuses every five years.8 Source: http://2010.census.gov/2010census/Why Do We Care? U.S. Congressional representatives are apportioned based on census counts.  Federal dollars are distributed based on census for schools, employment services, highway assistance, housing construction, hospital services, programs for the elderly, etc. Conducted every 10 years (now  a rolling census) An actual count of entire population categorized by various criteria The only source for spatially detailed demographic data with a consistent coast-to-coast data structure The most reliable, detailed, and consistent source for describing local areas: neighborhoods, cities, counties of time series demographic data available9How the Data Are Collected Collected from households through a mail survey conducted every decade For the 2000 Census (2000 Census Home Page) more than 285,000 census takers and support personnel  accounted for 118 million households and 275 million persons in the U.S. Two different census questionnaires are distributed: short-form questionnaire contains questions asked of everyone(summarized in Summary Tape File 1 (STF 1) for 1980 and 1990, Summary File (SF 1) for 2000) long-form questionnaire contains questions asked of a population sample (1/6 households)(summarized in Summary Tape File 3 (STF 3) for 1980 and 1990, Summary File 3 (SF 3) for 2000) The long form is being replaced in the 2010 Census by the American Community Survey (ACS).  This program will survey homes every month and provide updated statistics every year instead of every 10 years. The program begins in 2003.10What's Included: Information on Population, Employment & Housing Characteristics  Long Form: Sample Counts (STF 3/SF 3)Population CharacteristicsHousing CharacteristicsSocial CharacteristicsAge of HousingEducationHeating FuelCitizenshipFacilitiesAncestryVehiclesLanguageMortgage StatusDisabilityChildrenPlace of BirthEconomic CharacteristicsIncomeLabor Force StatusEmploymentPlace of WorkPublic AssistanceRetirement IncomeWhat's Included: Information on Population, Employment & Housing Characteristics  Short Form: 100% Count (STF 1/SF 1) 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 in Summary Files (SFs)Population CharacteristicsHousing CharacteristicsAgeTenureGenderValue or Contract RentRaceVacancy StatusHispanic OriginNumber of RoomsMarital StatusUnits in StructureHousehold TypeCongregate HousingHousehold Relationship12Census Geography and