Planning Analysis:
Using Census Data


Overview of the Census Bureau

The Census Web page is your one stop source for Census information and data: http://www.census.gov

Key Products:

Strategies for Census Data Analysis

All are factors in how you might approach using census data as an analytical tool

Purpose of the Census

A.  Political representation

Article 1, Section 2 of the Constitution requires decennial census--primary purpose to assign seats in the House of Representatives to the state. Also used to draw districts at the state & local level.

B.  Revenue Implications

Since WWII, federal aid programs and revenue sharing funds have been allocated by formulas that rely on census data--not just pop, but per capita income, unemployment rates, age of housing, etc. For example: in 1989, a total of $58.7 billion, $236 per capita was transferred from federal to state and local governments for formula grants.

C.  Difficulties in Counting/Data collection

Becoming increasingly difficult. more heterogenous - non-English speaking, homeless, etc. Nonresponse increasing -- 63 % in 1990, 75% in 1980 on first mailing

D.  Undercounting

Concerns increasing--particularly in undercount of minorities. Census bureau conducts a "post mortem" after each census. A series of studies of what worked well and what didn't. Reduction in undercount is a primary goal.

E.  Political Aspects of the Census

Questionnaire Content. Content determination through three stages: considered needs of users outside of federal gov, Bureau formed 10 interagency working groups, chaired by staff and organized along content lines, and OMB organized a federal agency council to advise OMB on census data needs.

Reporting the Data. This is less well documented and is based on user input in regional and local meetings.

Adequacy of Coverage: basically a political dispute over the accuracy of the data

Budget: Determines how well bureau gets to do its job. 1990 cost $2.58 billion

Organization of Census Data

Basically four universes: population, workers, housing, households.

Basic definitional units:

Housing sample universe

housing unit sample frame - mailed to addresses - strives for 100 percent sampling of housing units.

Household universe

defined by occupied housing units--actually consists of three intersecting universes:

1. occupied housing units

2. household groups living in those quarters

3. persons in the households

each has a separate set of characteristics, ie HU, # rooms, hh # persons, persons -- age

Population Universe

ultimate goal to obtain a complete population count - contains info on individuals abstracted from their household and housing contexts. variables include age, race, and sex Two key variables contain information on individual relationships with others: marital status and household relationship

Labor Force/Employment Universe

Defined on basis of population: persons who seek and hold jobs--key rational for defining as a separate universe is that jobs are held at a different location than place of residence.

Labor force: included both employed and unemployed persons who are available for work.

Separation of employment from the housing unit and place of residence makes local analysis difficult for this universe

Content of Questionnaire

Data collected by two different questionnaires: sample and 100% (hand out, forms if possible)

short form questionnaire - to most households

long form - to sample, includes short form questions and other questions answered by a sample of the pop. It is subject to sampling error

Household Linkage

Average household size=occupied housing units x persons per unit

Occupied housing units = noninstitutional population/persons per unit

Geography of the Census

Data are reported for 39000 jurisdictions and 7 million blocks nationwide.

The quality and quantity of information increases as the geographic scope increases. (hierarchy principle)

Pitfalls

1.  the same name may be applied to more than one spatial unit. For example: LA CMSA, LA-LB PMSA, LA urbanized area, LA county, LA city

2.  geographic areas at lower levels may be subdivided by higher level geographic units. A common example is split tract by city limit.

TIGER (topologically integrated geographic encoding and referencing system). based on topology, a branch of mathematics that describes the spatial relationships among points, lines, and areas in a two-dimensional plane. Each line segment and point is coded with a series of geographic identifiers (name of street, address ranges, l & l, potilitcal/statistical, etc). national file is 25 gigs/average county 5.4 megs

Comparability of Boundaries over time: Tracts are most stable, however, are changed occasionally. Goal to maintain tracts at around 4000, but range from 1500-8000. Published books show changes

 Two Forms of Census Data

1. Summary Tabulations

aggregated by geographic area. published in standard printed format and also available on CD-ROM (you'll get a chance to work with this)

2. Microdata (PUMS)

Public Use microdata samples. Randomly selected records from the sample questionnaires and contain the full set of data (raw numbers). Three sample rates--1:1000, 1:100, 5:100 -- smaller rate used for national sample, higher rates for local areas. Only available down to county or MSA level. 100000 min pop

Sampling and Accuracy

100% v Sample

Sample data are weighted up to reflect #'s in entire pop.

Rate: 1 in 6, higher rates for smaller areas (1 in2 for juris less than 2500)

is subject to sampling variability and error. Can calculate statistical si

Editing and Imputation of Basic Records

Census exercises editing procedures to improve data quality. Surveys are screened for missing or erroneous entries. Efforts made to catch before processing. CB uses two procedures: allocation and substitution.

Allocation:

Made in central processing to fill missing entries or to replace unacceptable entries.

Procedure is to replace blanks with info borrowed from a different household. Replacement is drawn from last complete questionnaire that had chars similar to the present case. Believed to yeild better results that missing values.

Substitution:

In some cases, entire record is missing for a housing unit or person. Can occur because of nonresponse or mechanical error. If CB believes the person or unit exists, a full set of characteristics is substituted for that record. Only applied to 100% data items.

Accounting for imputed info:

publishes tables of imputed cases

Undercount:

No adjustment made in 1990 or 2000. overall undercount is not important, is by geographic area. Effectively askes CB to generate substitution records for persons never directly observed or known to live at an address

Major Census Data Groupings and Linkages

 

Housing

Household

Population

Economic

Definitional unit

Housing unit

Occupied housing unit

Persons at usual place of residence

Economic status or behavior of persons

Major classifications linking to other bases

Occupied or vacant

Owner or renter occupied

Relationship in household, especially the householder

Total household income and poverty status

Person specific rates of behavior

Variables describing aggregate linkage

% occupied (or vacant)

% owner-occupants (ownership rates)

% in household

% householders (headship rate)

Persons per household (average HH size)

Median HH income

Per capita income

% families or persons below poverty level

% in labor force (LF participation rate)

Major classifications internal to each category

Structure type

Tenure

Size of unit (rooms)

Year built

Price

Family or nonfamily

-marital status

-presence of children

Size (number of persons)

Duration of occupancy

Age

Sex

Race and Hispanic origin

Marital status

Educational attainment

Labor force status

Occupation and industry

Individual income

Commuting behavior

Source: Analysis with Local Census Data, Myers, 1993

 

Census Geography for 1990 Data Files and Publications

A. Basic Hierarchy (with summary level codes)

010 United States

020 Region

030 Division

040 State (including D.C.)

050 County (or equivalent entities)

060 County subdivisions [minor civil division (MCD), census county division (CCD, and unorganized territory

070 Place (both incorporated and census designated)

080 Census tract and block numbering areas (BNA)

090 Block group

100 Block

-- Housing unit, institutional living quarters, or street shelter

B. Supplementary Geographic Areas

400 Urbanized areas; urban/rural areas

300 Metropolitan areas (MAs), including freestanding metropolitan statistical areas (MSAs), consolidated MSAs (CMSAs), and their component primary MSAs (PMSAs)

200 American Indian and Alaska Native areas

500 Congressional districts

800 ZIP codes

-- Traffic analysis zones

-- School districts

-- User-Defined Areas Program (UDAP)

Source: Analysis with Local Census Data, Myers, 1993


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October 07, 2003