Finding County-Based Data

from Hidden Sources

Lisa Neidert

Population Studies Center

University of Michigan

Three Problems

Produce county-based data from summary data Not all counties represented

Produce county-based data from microdata County identifiers are not in microdata

Produce county-based data from microdata County identifier in data Some county populations are too small for reliable

data

American Community Survey (ACS)

Replacement for the census long-form questionnaire

3,000,000 households a year County-level data every year

Not quite

ACS Products Schedule

Distribution of US counties by size

1,321

1,033

788

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1

65,000+

20.000 - 59,999

1 to 19,999

Statistics based on ACS 1-year data: Unit is county

Statistics based on ACS 3-year data: Unit is county

What are PUMAs?

Public Use Microdata areas

Combination of population geographies that sum to at least 100,000 population.

In rural areas, several counties will form a PUMA. In an urban area, a county will be subdivided into multiple PUMAs.

PUMAs do not cross state boundaries

Smallest geography available in the microdata.

Statistics based on ACS 3-year data: Unit is PUMA

Convert PUMA-based statistics to county-based statistics

PUMA-based statistic

Converted to county-based statistic

Example based on microdata

Previous example used a table from summary data Distribution of the baby boom population

Microdata allows user-generated table Distribution of earning equality among

couples

Where do couples have egalitarian earnings profiles?

Micro-data step

Where do couples have egalitarian earnings profiles?

Micro-data step Produce PUMA-specific results

Where do couples have egalitarian earnings profiles?

Micro-data step Produce PUMA-specific results Convert PUMA-based results to county-based

using cross-walk

What about microdata with county identifiers?

Identifiers on Natality Detail files 1968-1988 | all counties identified 1989-2005 | only counties > 100,000 2006+ | no state or county identifiers

Distribution of births by county (1988) <100 | 512 counties <500 | 1,998 counties <1000 | 2,498 counties

Some extreme cases Loving county, TX 2 births Hinsdale county, CO 3 births Petroleum county, MT 3 births

Solution

Cumulate small population counties by PUMA Calculate Fertility measures

Total Fertility Rate Timing of fertility events Non-marital childbearing

Use cross-walk to assign PUMA characteristic to counties

Finished Product

Future Directions

Cautionary Pseudo-county data Small population-based statistics County population may be incorrect weight

Web-based tool (PUMA to County) Input PUMA-based table Output County-based table GIS ready

Include indicator for multi-county PUMAs