Census 2000 PUMS Product Profile www.census.gov 1

a data products update from the U.S. Census Bureau

U.S. Department of Commerce

Economics and Statistics Administration

U.S. CENSUS BUREAU

Public Use Microdata Sample

2003 (PUMS) Files

PRODPR/03-3

Issued January 2004

www.census.gov

PUMS Files at

a Glance

• Detailed demographic

and housing data sets

for the advanced user

• Extracts of responses

from the Census

2000 long-form

questionnaire

• Complete U.S.

coverage through

Public Use Microdata

Area (PUMA)

geographies, plus

Puerto Rico

• Downloadable files

on the Web through

File Transfer Protocol

or purchase on

CD-ROM/DVD

• Customizable data

Need Data to Do Your Own

Research?

If you are looking to create your own custom

tabulations using decennial census data, then

the Public Use Microdata Sample (PUMS) files

are just what you need. PUMS files show the

full range of responses from the long-form

questionnaires, for example, how one household or one household member answered

questions on occupation, place of work, and so

forth. The files contain records for a sample of

all housing units, with information on the

characteristics of each unit and/or each person

in it. The user actually sees the responses

made by a household — with certain modifications.

All identifying information is removed to ensure

confidentiality. The records selected are a

sample of those households that received the

questionnaire. The questionnaire included

questions on age, sex, tenure, income, education, language spoken at home, journey to

work, occupation, condominium status, shelter

costs, vehicles available, and other subjects.

The full range of population and housing

information collected in Census 2000 is

available in the PUMS: over 450 occupation

categories, age by single years up to 89, and

so forth.

Why Use PUMS?

For many data users, the Census 2000 Summary Files and tabular profiles will suffice.

Microdata are for those users who want to

create do-it-yourself tabulations, to be able to

further draw on the richness of detail recorded

in the census.

Who Can Use PUMS?

Microdata users frequently want to look at

relationships among variables not shown in the

Summary File products offered by the Census

Bureau. For example, what characteristics do

families with four or more children have in

common? What are the incomes at different

educational attainment levels? The advantage

of PUMS is that data users can tabulate data

according to the characteristics they need to

know.

PUMS files are perfect for people, such as

students, who are looking for greater accessibility to inexpensive data for research projects.

Data users in academic life — economists,

psychologists, and sociologists — have found

the PUMS useful for regression analysis and

modeling applications.

Figure 1.

PUMS Products/File Types

 Public Use Microdata File Types

1-percent file 5-percent file

Data detail Most detail in PUMS files Some detail filtered out

for confidentiality

reasons

Geography 400,000 population 100,000 population

threshold Super-Public threshold Public Use

Use Microdata Areas Microdata Areas

(Super-PUMAs) (PUMAs)
Census 2000 PUMS Product Profile www.census.gov 3

Confidentiality Issues

Because of the rapid advances in

computer technology and the increased

accessibility of census data to the user

community, the Census Bureau has had

to adopt more stringent measures to

protect the confidentiality of public use

microdata through disclosure-limitation

techniques. At the same time, the

Census Bureau recognizes the needs of

data users for greater characteristic

detail and greater geographic specificity. Hence, two sets of files are produced: one that provides a fuller

range of detailed characteristics (the

1-percent files) and one that provides

greater geographic detail, but less

characteristic detail (the 5-percent files).

In the Public Use Microdata Samples,

confidentiality is protected by the use of

the following processes: data-swapping,

top-coding of selected variables,

geographic population thresholds, age

perturbation for large households, and

reduced detail on some categorical

variables.

Data swapping is designed to protect

confidentiality in tables of frequency

data (the number or percent of the

population with certain characteristics).

Data swapping is done by editing the

source data or exchanging records for a

sample of cases. Swapping is applied to

individual records and, therefore, also

protects microdata.

Top-coding is a method of disclosure

limitation in which all cases in or above

a certain percentage of the distribution

are placed into a single category.

Geographic population thresholds

prohibit the disclosure of data for

geographic units with population counts

below a specified level. (See descriptions of Public Use Microdata Areas

(PUMAs) and super-PUMAs).

Age perturbation, that is, modifying the

age of household members, is required

for large households (households

containing ten people or more).

Detail for categorical variables is

collapsed, if the categories do not meet

a specified national minimum population threshold.

Geography of the

1-Percent PUMS File

The 1-percent PUMS files provide

users the maximum amount of social,

economic, and housing information

available. There is no national

minimum threshold for the

identification of variable categories,

with the exceptions of a national

minimum population of 8,000 for

race and Hispanic origin. The goal

of these files is to provide a similar

level of detail, as was available in

the 1990 PUMS files.

In order to provide the level of

characteristic detail for the 1-percent

files described above, the minimum

population threshold needed to be

raised above 100,000 (the Public

Use Microdata Area (PUMA)

minimum). A new geographic entity

was created — the super-PUMA.

Super-PUMAs have a minimum

population of 400,000 and are

composed of a PUMA or PUMAs.

(PUMAs are shown only in the 5-

percent files. Super-PUMAs are

identified in both the 1-percent

and 5-percent files.) Each state is

identified, and any state with a

population of 800,000 or greater

can be subdivided into two or more

super-PUMAs. Super-PUMAs and

PUMAs do not cross state lines.

Geography of the

5-Percent PUMS Files

The 5-percent PUMS files provide

data for both PUMAs — geographic

entities with a minimum population

of 100,000 — as well as superPUMAs. The minimum PUMA

threshold was held at 100,000 by

increasing the degree of variable

collapsing. To maintain

confidentiality, while retaining as

much characteristic detail as

possible, a minimum threshold of

10,000 in the national population is

set for the identification of variable

categories within categorical

variables in the 5-percent files.

The 1-percent files contain

geographic equivalency files

showing the relationship between

super-PUMAs and standard Census

2000 geographic concepts (e.g.,

counties, etc.). The 5-percent files

contain geographic equivalency files

showing the relationships among

super-PUMAs, PUMAs, and standard

Census 2000 geographic concepts.

In addition, maps of super-PUMAs

and PUMAs are available at:

http://www.census.gov/geo

/www/maps/puma5pct.htm.

Figure 3 below illustrates a map,

accessible online in PDF format, of

the 1-percent super-PUMA areas

available for the state of

Connecticut.

Figure 3.

1-Percent Super-PUMAs for Connecticut
2 www.census.gov Product Profile Census 2000 PUMS

Summary Data and

Microdata — What’s the

Difference?

Summary data are predefined cross

tabulations of characteristics. The basic

unit of analysis is a specific geographic

entity — state, county, etc. — for which

estimates of persons, families, households, or housing units are provided.

The Census Bureau has created the

tables that users say they need — but

users occasionally need tabulations not

covered in the standard data products.

It is you, the user, who determines the

structure of the tabulation and the

characteristics to be tabulated in the

PUMS files.

In microdata, the basic unit is an

individual housing unit and the people

who live in it. The record shows all the

information associated with a specific

housing unit, except for names, addresses, or other identifying information.

Only large geographic areas are identified on microdata records. These

geographic entities are delineated

specifically for this product. The Census

Bureau uses a minimum population

threshold to help avoid disclosure of

information about any household or

individual.

To further protect confidentiality, there is

limited detail on items such as place of

residence, place of work, high incomes,

and other items.

PUMS Records

There are two basic record types: the

housing unit record and the person

record. Each has a unique identifier. Each

of the records contains a serial number

that links the persons in the housing unit

to the proper housing unit record. The

file is sorted to maintain the relationship

between both record types.

The Census Bureau releases the PUMS in

this format because of the tremendous

amount of data contained in one record.

Although these records are extremely

large, they can be handled by most

statistical or report-writing software.

Each record has an individual weight

that allows users to produce population

estimates close to those in other

products showing sample data.

How Are the Microdata

Provided?

The U.S. Census Bureau provides two

sets of Public Use Microdata Sample

(PUMS) files: 1-percent state files and

5-percent state files. These files provide

the greatest possible detail, while

protecting the confidential nature of the

data. For Puerto Rico, 1-percent and

5-percent files also are created. For

Guam and the U.S. Virgin Islands, a

10-percent file was created for each

island area.

Figure 2.

PUMS Records

Items on the housing record include: Items on the person record include:

• Bedrooms

• Condominium fee

• Contract rent

(monthly rent)

• Cost of utilities

and fuels

• Family income

• Family, subfamily,

and household

relationships

• Fire, hazard, and

flood insurance

• Gross rent

• House heating fuel

• Household income

• Household type

• Kitchen facilities

• Linguistic isolation

• Meals included in

rent

• Mortgage status and

selected monthly

owner costs

• Plumbing facilities

• Presence and age of

own children

• Presence of subfamilies

in household

• Property value

• Real estate taxes

• Residence state

• Rooms

• Telephone service

• Tenure

• Units in structure

• Vacancy status

• Vehicles available

• Year householder

moved into unit

• Year structure built

• Ability to speak

English

• Age

• Ancestry

• Citizenship

• Class of worker

• Disability status

• Educational attainment

• Hispanic origin

• Hours worked

• Income by type

• Industry

• Language spoken at

home

• Work status

• Marital status

• Means of transportation

to work

• Migration

• Years of military

service, veteran

period of service

• Mobility status

• Occupation

• Personal care

limitation

• Place of birth

• Place of work

• Poverty status

• Race

• Relationship

• School enrollment

and type of school

• Sex

• Time of departure

 for work

• Travel time to work

• Vehicle occupancy

• Weeks worked

• Work limitation

status

• Year of entry
4 www.census.gov Product Profile Census 2000 PUMS

These maps are available at http:/

/www.census.gov/geo/www/maps

/sup_puma.htm.

Additionally, maps for PUMAs and

super-PUMAs can be found in the

reference maps area of the Census

Bureau’s main online data

dissemination tool, the American

FactFinder®(AFF). While most

decennial census data are in AFF,

PUMS data are available only by

file transfer protocol download or

from a CD-ROM or DVD.

Figure 4 illustrates the PUMAs and

super-PUMAs for Connecticut using

the reference mapping function of

American FactFinder®.

Population Thresholds for PUMAs

Each geographic unit in the 5-percent

files — PUMAs — must meet a

minimum population threshold of

100,000. The minimum PUMA

threshold is held at 100,000 people

by increasing the degree of variable

collapsing to an appropriate level to

maintain confidentiality. The 100,000

minimum population threshold allows

for a wide variety of local-level

geographic analyses, such as studies

of nonmetropolitan, metropolitan, and

intrametropolitan areas, conducted by

public agencies, academic researchers, and others in the private sector.

The 100,000 minimum population

threshold — the threshold set for both

the 1980 and 1990 PUMS files —

permits historical comparability.

Minimum Population Threshold for

Categorical Variables

To maintain confidentiality, while

retaining as much characteristic detail

as possible, a minimum threshold of

10,000 in the national population is

set for the identification of groups

within categorical variables in the

5-percent PUMS files.

Post-Processing

To provide more precise means of

protecting confidentiality so that as

much detail as possible can be

included, the 5-percent file variable

collapsing requirements are determined after the microdata samples

have been drawn. Each variable is

analyzed, and only those values that

Figure 5 shows the basic table layout

functionality of the proprietary software.

Download PUMS on the

Internet

The Census Bureau has a File Transfer

Protocol (FTP) Web site that allows users

to download data sets for various

products. Many of the standard

decennial data products are available

for download from the site. To ease the

download burden, the data are typically

broken down by state and then the files

are segmented and compressed. Users

download the zipped files to their own

computers where they must then be

decompressed or unzipped and

reconstructed into a master file. Several

of the downloadable products can then

be manipulated using common spreadsheet or database packages.

The Public Use Microdata Files are more

complex and require a higher level of

sophistication for downloading. The

PUMS FTP files are broken down by

state and are offered in compressed

and noncompressed formats. The files

are presented as a compressed .zip file

or a noncompressed .dat file. These

files are designed to work with more

advanced statistical software packages

and may be too cumbersome for

standard spreadsheet and database

applications.

do not meet the 10,000 minimum

national population threshold are

collapsed into more general categories.

Buy PUMS on CD-ROM or DVD

If you’d like to get all the data for your

state, including software to access and

manipulate it, then a CD-ROM or DVD is

the tool for you. The CD-ROM and

DVDs are also beneficial in alleviating

long download times for PUMS data

from the Internet. You may purchase

discs from the Census Bureau’s Customer Services Center at

301-763-INFO (4636).

The files on the disc come with proprietary software that operates on computers with Microsoft Windows

95/98/2000/NT/ME/XP operating

systems. The software uses a step-bystep approach to creating the desired

extract with a tabular interface. You

begin by selecting the data element of

the extract you need to use, and then,

you build your variables from there.

Drag-and-drop functionality is used

when it comes to moving data elements

or the various ‘dimensions’. Among

many functions, users can create

percentage distributions, perform

calculations, and apply different weighting factors to the data.

Figure 4.

Reference Map in Amercian FactFinder® Illustrating the

1-Percent and 5-Percent PUMA and Super-PUMA Boundaries
Census 2000 PUMS Product Profile www.census.gov 5

For FTP purposes, the url is http://

ftp2.census.gov/census_2000

/datasets/PUMS/

For standard Web downloading, the url

is http://www2.census.gov

/census_2000/datasets/PUMS/

Other Public Use Microdata Files

Several of the Census Bureau’s other

data collection programs provide Public

Use Microdata Files. These programs

include:

• American Community Survey

• Survey of Income and Program

 Participation

• American Housing Survey

• Vehicle Inventory and Use Survey

• Current Population Survey

Many of these microdata files are

available online at www.census.gov

through the data dissemination utility

known as the Federal Electronic Research and Review Extraction Tool

(FERRET). FERRET is an advanced

software tool used to make extracts

from the various data sets.

For More Information About Public

Use Microdata Samples and Other

Census 2000 Data Products

• Visit the Census Bureau’s Internet site

at www.census.gov or call our

Customer Services Center at

301-763-INFO (4636).

• Visit your local library. Many major

university and public libraries

participate in the Federal Depository

Library Program and receive copies

of Census Bureau reports and discs.

• Call or visit one of 1,800 state and

local planning groups, libraries,

chambers of commerce, and others

that participate in a Census Bureau

data center program. For a complete list see www.census.gov/sdc

/www/.

Figure 5.

Creating Extracts Using the CD-ROM/DVD Software

• Call or visit a Census Bureau Regional

Office. For the address and phone

number of the regional office near

you, visit: www.census.gov/field

/www/.

Stay Current

To keep up with the release of the

microdata discs and maps, as well as

other Census Bureau products, users

can subscribe to the Census Product

Update, a biweekly newsletter available

free online or in abbreviated form

through email. To view the newsletter or

subscribe go to http://www.census.gov

/mp/www/cpu.html.
6 www.census.gov Product Profile Census 2000 PUMS

File

Summary

File 1

(SF 1)

Summary

File 2

(SF 2)

Summary

File 3

(SF 3)

Summary

File 4

(SF 4)

Source

Decennial census

short form

Decennial census

short form

Decennial census

long form

Decennial census

long form

Data

Population, age, sex, race,

Hispanic-origin, household

relationship, tenure (owner/

renter), group quarters

Same as SF 1; tables are

repeated for 249 race and

Hispanic-origin groups

Population, age, sex, race,

Hispanic-origin, household

relationship, marital status,

education, employment status,

occupation, industry, income,

poverty status, citizenship,

foreign-born, year of entry,

ancestry, disability, migration,

place of work, language spoken

at home, ability to speak English,

journey to work, veteran status.

housing tenure, value, mortgage

status, rent, plumbing, kitchen

facilities, occupants per room,

real estate taxes, units in

structure, bedrooms, heating

fuel, monthly owner costs, year

structure built, year household

moved in, vehicle availability

Same as SF 3, but fewer tables;

tables are repeated for 336 race,

Hispanic-origin, and ancestry

groups. First detailed data on

occupation and industry.

Tables

Total: 286

Population tables: 230

Housing tables: 56

Total: 47

Population tables: 36

Housing tables: 11

Total: 813

Population tables: 484

Housing tables: 329

Total: 323

Population tables: 213

Housing tables: 110

Smallest

geography

Census block

Census tract

Block group

Census tract

Other Census 2000 Data Products: Summary Files at a Glance
Census 2000 PUMS Product Profile www.census.gov 7

Appendix I.

Additional Specifications for the

PUMS Files

Additional PUMS file specifications are

included for the following variables in

the 1-percent and 5-percent files.

Dollar Amounts

Dollar amounts are rounded before all

summations, ratio calculations, or

presentations of amounts. The dollar

amounts are represented, including

negative amounts, in Figure 6.

This rule is applied to income types,

utility costs, mortgage costs, rent,

condominium fees, hazard insurance

costs, and mobile home fees.

Implementing income top-coding. An

individual’s income is rounded on a

graduated scale and independently

top-coded by variable type. The value

inserted for observations at and above

the top-code is the state mean of all

cases at and above the top-code

minimum value.

Housing-related dollar amount variables.

Property taxes are categorized in a

similar way to 1990, with the exception

of the higher tax categories. The

categories for the 5-percent file are

collapsed in order to protect

confidentiality.

All other housing-related dollar amounts

are treated similarly to income (see

above). That is, the variables use the

same rounding scale as for income, and

each case receives the state mean of

top-coded cases for each respective

variable.

Race and Hispanic-Origin Data

For the first time in Census 2000,

respondents were allowed to mark

more than one race. Whether someone

is Hispanic or Latino was asked as a

yes/no question separate from the race

question. Data on race include “yes/no”

variables for the five Office of

Management and Budget (OMB) races

[White, Black or African American,

American Indian and Alaska Native,

Asian, and Native Hawaiian and Other

Pacific Islander] and Some other race on

both the 1-percent and the 5-percent

files. Presenting the microdata in this

manner will allow data users to

construct the 63 possible race

combinations.

In addition, both the 1-percent and

the 5-percent files will show all

combinations of the 15 race categories

shown on the census questionnaire,

specific American Indian and Alaska

Native tribes alone, and detailed Asian

and Native Hawaiian and Other Pacific

Islander groups alone that meet the

relevant thresholds. In the 1-percent

file, there is a national minimum

population threshold of 8,000 for the

identification of categories in the race

and Hispanic-origin variables; in the

5-percent files there is a national

minimum population threshold of

10,000 for the identification of

categories in these variables. For

example, the racial category “Black or

African American and Filipino” is shown

on both files, because there are more

than 10,000 people in the United States

who reported this combination on

Census 2000.

Age Detail

For both the 1-percent and 5-percent

files, single-year age categories are

provided through age 89. There is one

nationwide top-code (age 90) and each

state receives the mean age of

individuals in the state 90 years and

over.

Ancestry Variables

The Census Bureau codes up to two

responses for the ancestry question.

For the 5-percent file, if the combined

total national population from both of

these responses for an ancestry group

is 10,000 or greater, that group is

identified by itself in both the first

response and second response

variables, even if the total for the

category in either or both of the

individual ancestry variables does not

meet the 10,000 threshold.

Industry and Occupation

Two sets of codes for each occupation

and industry are provided: (1) the

census code and the Standard

Occupational Classification (SOC)-based

code for occupation and (2) the census

code and the North American Industry

Classification System (NAICS)-based

code for industry.

Continuous Variables

Continuous variables are treated the

same on both files. Additional

specifications for departure time (when

a person usually left for work in the

week before their census form was

filled out) and year of entry into the U.S.

are described below.

Dollar amounts Rounded dollar amount

No income $0

$1-$7 $4

$8-$999 round to the nearest $10

$1,000-$49,000 round to the nearest $100

$50,000 or more round to the nearest $1,000

Departure time is categorized as

follows:

12 midnight - 2:59 a.m., in 30-minute

increments

3 a.m. - 4:59 a.m., in 10-minute

increments

5 a.m. - 10:59 a.m., in 5-minute

increments

11 a.m. - 11:59 p.m., in 10-minute

increments

Year of entry into the country will

have a bottom-code of 1910.

Figure 6.

Represented Dollar Amount
Overseas Service — add $25.00

Check payable to Commerce-Census

 9 Census deposit account

METHOD OF PAYMENT (please check one) VISA, MasterCard, AMEX, or Discover account number:

Expiration date: Month/Year: /

Name on card:

Signature:

TOTAL $

To place your order by phone (have your credit card ready) or for further information about PUMS data products, please call our Customer Services

Center at 301-763-INFO (4636), fax your order toll-free to 888-249-7295, or access our Web site at http://www.census.gov and select “Catalog.”

For mail orders only, complete this order form and send it with your payment to: U.S. Department of Commerce

U.S. Census Bureau (MS 0801)

P.O. Box 277943

Atlanta, GA 30384-7943

Name: Date:

Company:

Address:

Phone: ( ) Fax: ( )

E-mail address:

Order Form

Yes! I want the Census 2000 Public Use Microdata

Sample Files (PUMS). Please send me the CD-ROMs

and/or DVDs I have chosen below. I have enclosed

$ (check or money order only) for my

selection or provided credit card information below.

(City, state, ZIP Code) (No P.O. boxes)

Software

provided Price Quantity Total

PUMS 1%: U.S. on CD-ROM None— ASCII Format $50

PUMS 1% and 5%: U.S. on DVD-ROM Yes $70

PUMS 1%: U.S. on CD-ROM Yes $50

PUMS 10%: Guam on CD-ROM None— ASCII Format $50

PUMS 10%: Virgin Islands on CD-ROM None— ASCII Format $50

SUBTOTAL $

Product