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How do the ACS Five-Year Migration Data Compare to the 2000 Census Migration Data?

Written by:
Working Paper Number SEHSD-WP2012-14

Introduction

From 1940 to 2000, the long form of the Decennial Census asked respondents about their migration patterns. The Census Bureau provided the public with an array of origin-destination migration flow data products, over the decades. The county-to-county migration flows, in particular, have continued to be a staple product. For Census 2000, a migration DVD with counts of movers was produced that contained a county-to-county flow table, and tables of mover counts by characteristics.

After Census 2000, the long form data was replaced by the American Community Survey (ACS). The 2010 Census and future decennial censuses have no migration data, making the ACS a primary source of migration data. ACS started collecting data in 1996 in four test sites. The scope of the survey grew and beginning in 2005 the survey sampled housing units in all counties in the U.S. and Puerto Rico. Group quarters (e.g., college dormitories, prisons, nursing homes, military barracks) were added to the sample in 2006.

One major difference between the Census and the ACS migration questions is the time reference for the question asked about a between the previous residence and the current residence. Census 2000 asked where the person lived 5 years ago (as of April 1, 1995) while the ACS asks where the person lived 1 year ago. The time period was changed to reflect the on-going data collection of the ACS, and allows for annual estimates of geographical mobility.

The Census Bureau released county-to-county migration estimates for the first time using the ACS in March 2012. The working paper and data release provide the county-to-county flow and mover counts. This paper further analyzes the relationship of ACS migration data compared with the 2000 Census data. Because the ACS is the new source for migration data, it is important that these estimates are sound. This analysis looked for stability in the numbers, but also for reasonable changes in the data. As the estimates are determined reasonable, then mover characteristics are provided using ACS data.

We are expecting to find a larger number of movers in the 2000 Census data because it includes movers who moved between 1 and 5 years ago. We are also predicting that most of the county-to-county migration flow ratios will be relatively similar, though some outliers are expected.

Downloadable Poster

This poster analyzes 5-year county- to-county migration data from the 2005-2009 ACS through flow and mover counts. These counts are compared to the 2000 Census data to show that the ACS 5-year data are valid estimates of county-to-county migration.

Documentation and Analysis

Table Notes

Sample size and data quality measures (including coverage rates, allocation rates, and response rates) can be found on the American Community Survey website in the Methodology section.

Data are based on a sample and are subject to sampling variability. The degree of uncertainty for an estimate arising from sampling variability is represented through the use of a margin of error. The value shown here is the 90 percent margin of error. The margin of error can be interpreted roughly as providing a 90 percent probability that the interval defined by the estimate minus the margin of error and the estimate plus the margin of error (the lower and upper confidence bounds) contains the true value. In addition to sampling variability, the ACS estimates are subject to nonsampling error (for a discussion of nonsampling variability, see Accuracy of the Data). The effect of nonsampling error is not represented in these tables.

Page Last Revised - October 8, 2021
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