# Presentation: 883900

## Population Association of America

- Annual Meeting
- Los Angeles, CA
- March 23, 2000

## The American Community SurveyExploring a New Data Source for the Study of Migration

- Jeffrey J. Kuenzi
- Population Division
- Journey to Work and Migration Statistics Branch

## Introduction

- The American Community Survey (ACS) is a developmental program designed to potentially replace the decennial census long form in 2010.
- As the major source of small area migration data with demographic detail, the phase-out of the long-form has important implications for migration research.
- ACS data will also open up interesting new migration-related research opportunities.

## ACS and Migration Statistics

- Background and Implementation
- Comparison to Decennial
- Yearly Small Area Migration Data

## Background

- The ACS will cover the same topics as the long form, providing detailed economic, social and housing profiles of communities throughout the U.S.  However, this data will be collected continuously, instead of once every ten years.
- The ACS will draw on a nationwide sample of about 3 million addresses.  The design is a “rolling” sample survey contacting a different set of addresses each month.  Once sampled, a housing unit will not be back in the sample for at least five years.

## Implementation

**  ****1996 - 1998** 	***Demonstration period*** in selected sites (four in 1996, eight in 1997, and nine in 1998).
**  ****1999 - 2002** 	Thirty-one ***comparison sites*** with 5 percent annual samples.
**  ****2003 - on** 	***Full implementation*** nationwide (sampling about 3 million addresses per year including all counties).

## Comparison to Decennial Design

- Data Collection Period
- Migration Interval
- Data Pooling

## Data Collection Period

- ACS data are collected throughout the year, including each person at his/her current residence at the time of interview.  For example, the Census Bureau conducted the 1998 ACS from January 1998 through December 1998.
- The decennial census collects data in the few months around Census Day (April 1), counting each person at his/her usual residence as of census day.
- Thus, instead of a single “snap-shot” of the whole population at one time, we get a series of pictures of the population throughout the year.  The series will create a yearly “average” for the population – a fuzzier, “moving” image for place of residence.

## Migration Interval

- As on the long form, the migration question on the ACS instrument asks respondents to give their “residence 5 years ago”.  (This was changed to a one-year interval in 1999.)
- Due to the rolling nature of the ACS sample, the beginning of that 5-year period shifts with the reference date.
- For example, those interviewed in November of 1996 were asked where they lived in November of 1991, while respondents in December of 1998 were asked about December of 1993.

## Data Pooling

- The sampling strategy for the ACS is such that, for small areas, data must be pooled over multiple survey years in order to produce sufficiently robust sample sizes.
- To get accurate estimates for areas with populations under 65,000, between two and five years of data are needed.
- For basic descriptive statistics data users must pool data according to the total population of the area; these recommendations are presented in Table 1.

## Table 1: Years of Data Required to Generate Accurate Estimates

## Comparison to Decennial Estimates

- ACS data from the demonstration period are currently available to the public.  CD-ROMs for 1996, 1997 and 1998 have been released which include summary tables and microdata.
- Additional data and information are available through the Census Bureau’s ACS website as well as the American Factfinder website (see reference information on the last panel of this presentation).
- Table 2 compares migration data from the 1990 census to  the 1996, 1997 and 1998 ACS surveys.

## Table 2: Decennial and ACS Migration Estimates for Multnomah County, OR

## Yearly Small Area Migration Data

- The migration data currently available are limited in their timeliness and geographic detail.
- Decennial data are collected too infrequently to detect short-term changes in migratory patterns.
- National-level survey data (e.g. CPS and SIPP) have inadequate sample sizes for small area analysis.
- Administrative data lack the demographic detail necessary to address many key research questions.

## ACS Data Fills the Void

- ACS represents an exciting new source of data for research in the field of migration.  For the first time, detailed information on migrant populations will be available at small levels of geography in intercensal years.
- The following panels present a series of maps that display tract-level in-migration to Multnomah County, Oregon.  The degree of shading represents the proportion of each tract’s population who are migrants from another state.
- The lightest shade of pink represents tracts where the migrant population makes up less than 10% of the population, while tracts colored with the darkest shade are composed of more than 30% migrants.

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## Conclusion

- While these maps simply show the flow of in-migrants to this area, they could also be used to display the characteristics of in-migrants.  Thereby providing a spatial analysis that would address questions such as: What is the educational attainment of recent migrants to the metro area?  How is population redistribution changing the racial/ethnic composition of the area?  Are low-income portions of the metro area being gentrified by wealthier new-comers?  Future research using ACS will undoubtedly address these and other important questions.

## For more information about ACS

- E-mail: 			ACS@Census.Gov
- Postal address: 	U.S. Bureau of the Census
- 			FOB-3, Room 1657
- 			Washington, DC  20233
- Telephone: 	   	(888) 456-7215
- ACS home page:	http://www.census.gov/acs/www
- American Factfinder:	http://factfinder.census.gov)
- To order data files:	301-457-4100