Publically Available Migration Data
Based on Administrative Records:
A Discussion of Current and Future Data and Methods
Caleb Miller
Population Division
United States Census Bureau
For presentation at The 2010 Annual Meeting of the
Association of Public Data Users
Washington, DC
September 20, 2010
This paper is released to inform interested parties of research and to encourage
discussion. Any views expressed on methodological issues are those of the
author and not necessarily those of the U.S. Census Bureau.
Outline
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Overview
Data/Methods
Current Products
Analysis
Future Plans
Summary/Conclusion
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Overview
• This session, “Tracking Population Migration,” sponsored by the
Association of Public Data Users, focuses on population migration.
• The Internal Revenue Service (IRS) and the U.S. Census Bureau work
together to produce a publically available migration product.
– Distributed by the IRS on the IRS website
• http://www.irs.gov/taxstats/article/0,,id=212695,00.html
• Free data post 2005
• Pay for data pre 2005
• This presentation will discuss the inter-agency relationship, data and
methods used to build this data product as well as future plans.
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Overview
• The U.S. Census Bureau is allowed access to annual tax return data to
support our mission of developing federally mandated, annual
population estimates for the nation’s states and counties.
- We use these data to produce domestic migration rates for use
within the cohort component model of population estimation.
- The data displayed in this presentation differ from the Population
Division’s official domestic migration statistics.
- Tax data allow the U.S. Census Bureau to measure the geography
and frequency of domestic migration.
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Data/Methods
• The IRS produces an annual data extract for the Census Bureau that
contains administrative data collected for every 1040 tax form
processed by the IRS. The data contain:
– Tax Filing Units
• The filer and spouse of filer, plus all exemptions represented
on the forms.
– Nine Digit Zipcode
• ZIP+4
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Data/Methods
• The total number of exemptions per tax return is based on the total
number of exemptions reported by the filer.
– A ‘Return-based’ migration totals method.
– Different from a ‘Person-based’ method described later.
– The geography of exemptions are based on the address listed on
the tax return.
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Data/Methods
• The nine digit zipcode associated with a tax return, used to
represent where the tax filer and his/her exemptions live, is
geocoded using a ZIP+4-to-county correspondence file.
– The file contains all the ZIP+4s for a given state and/or
county and/or statistical equivalent.
• Geocoding the tax data with the correspondence file allows one
to determine the geography of migration.
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Data/Methods
• Consecutive year tax data, X to X+1, is matched.
– Residence in Year X = Migration Origin
– Residence in Year X+1 = Migration Destination
– If Residence in Year X = Residence in Year X+1 then no
migration has taken place (non-migrants).
– If Residence in Year X ≠ Residence in Year X+1 then migration
has occurred (migrants).
• The total number of in-migrants, out-migrants, and non-migrants for a
given level of geography (U.S. , state, and county) are determined by
the summation of individual tax exemptions at that level of
geography.
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Current Products
• Once the tax data have been received, geocoded, matched, aggregated
and suppressed by the U.S. Census Bureau, a final dataset is prepared
for the Statistics of Income Division of IRS (SOI) .
– Data suppression is introduced to protect the confidentiality of
individual taxpayer data.
• The data contain the total number of returns and exemptions for non-,
in-, and out-migrants for a given level of geography; state and county.
• The data contain geographically specific in- and out-migration flowtotals for a given level of geography; county-to-county and state-tostate.
– For example, the number of returns and exemptions flowing from
Baltimore County, Maryland to New York County, New York.
• SOI formats and prepares the data for public release.
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Analysis
• Migration is closely related to age, population change, and economic
conditions.
• Migration statistics provide rich information about demographic and
economic processes.
• The following four slides will show how IRS migration statistics help
researchers and analysts understand levels and trends in demographic,
geographic, and economic processes.
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Table 1. Metro Areas w ith the Largest Percentage Increases in Gross Out-m igration: 2004 to 2009
Percentage
Change in Net
Change in InGross Out-m igration
Increase
Migration
Migration
Metro Area
2004
2009
Palm Coast, FL
2,687
Cape Coral-Fort Myers, FL
15,485
St. George, UT
4,822
Lakeland-Winter Haven, FL
17,760
Hinesville-Fort Stew art, GA
8,331
Phoenix-Mesa-Scottsdale, AZ
99,948
Sebastian-Vero Beach, FL
4,043
Ocala, FL
9,144
Las Vegas-Paradise, NV
50,381
Bend, OR
5,705
Source: IRS Return-based Migration Data
5,566
28,873
7,583
27,063
12,486
147,150
5,926
13,250
72,222
8,163
107.1
86.5
57.3
52.4
49.9
47.2
46.6
44.9
43.4
43.1
-4,092
-18,672
-3,507
-8,258
83
-38,732
-2,702
-6,576
-39,086
-3,350
-1,213
-5,284
-746
1,045
4,238
8,470
-819
-2,470
-17,245
-892
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Table 2. Metro Areas w ith the Largest Percentage Increases in Gross In-m igration: 2004 to 2009
Percentage
Change in Net
Change in OutGross In-m igration
Increase
Migration
Migration
Metro Area
2004
2009
Odessa, TX
4,839
El Paso, TX
19,803
Grand Junction, CO
6,109
Hinesville-Fort Stew art, GA
8,791
Huntsville, AL
14,885
Midland, TX
5,857
Spartanburg, SC
8,159
Yakima, WA
5,598
Casper, WY
3,340
Columbus, GA-AL
18,829
Source: IRS Return-based Migration Data
7,527
30,223
9,091
13,029
21,610
8,445
11,619
7,886
4,653
26,174
55.5
52.6
48.8
48.2
45.2
44.2
42.4
40.9
39.3
39.0
1,429
3,876
1,417
83
3,605
862
1,336
1,970
408
2,094
1,259
6,544
1,565
4,155
3,120
1,726
2,124
318
905
5,251
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Future Plans
• In 2007, the Census Bureau’s Population Division moved from a
‘return-based’ system to a ‘person-based’ system of quantifying
migration to enhance estimates accuracy.
– Return-based: The total number of exemptions reported by the tax
filer was used to determine the number of exemptions for that tax
return at that level of geography.
– Person-based: The total number of exemptions are based on the
number of people listed.
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Future Plans
• Measuring migration at the person level, as opposed to the tax return
level, allows one to estimate migration during major life-course
events:
– Filing your 1st tax return, marriage, divorce, etc.
• Post 2010, the Census Bureau plans to provide ‘person-based’
migration total-flows by estimates geography to the IRS instead of the
‘return-based’ totals.
– Data will provide a more accurate representation of actual
migration totals and flows.
– The number of tax returns will no longer be reported
• The Census Bureau’s Population Division does not produce
household level migration statistics.
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Conclusion
• Migration research is critical in studying population change because
migration re-distributes existing population throughout space and
time.
• IRS migration data, representing approximately 80% of the U.S.
population, is the largest administrative records based data source to
estimate migration.
• The move from a ‘return-based’ to a ‘person-based’ migration product
is based on enhancing estimates accuracy.
– Data is more in line with official Census Bureau population
estimates methodology and data products.
– Quantities of migration are based on the actual number of people
moving; not based on number of people reported moving by the
tax filer.
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Contact information
Caleb M Miller
(301) 763-3529
caleb.m.miller@census.gov
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