How to read the data

What is counted

The IRS matches individual income tax returns filed in one calendar year with returns filed by the same taxpayers the next year. When the address on the second return sits in a different county from the first, the return counts as a move from the first county to the second. A return that stays in the same county, even after a move across town, counts as a non-migrant.

Three numbers come with every flow:

• Returns: the number of matched returns. One return is roughly one household.
• People: the number of exemptions or individuals listed on those returns, a stand-in for the number of people.
• Adjusted gross income: the total AGI on those returns, taken from the second year’s return and published in thousands of dollars.

Years

A period such as “2022–23” means returns filed in 2022 matched with returns filed in 2023, which mostly report income earned in 2021 and 2022. The site uses four periods: 2019–20, 2020–21, 2021–22 and 2022–23. For 2022–23 the IRS changed its matching method slightly, which the IRS says adds about 5% to the number of returns included. Changes between 2021–22 and 2022–23 therefore mix real change with the method change. In the 2020–21 and 2021–22 files no Connecticut counties appear, and from 2022–23 Connecticut is reported by its nine planning regions instead of its eight old counties, so Connecticut profiles show one year only.

What is left out

• People who do not file a federal income tax return, and returns that could not be matched across both years.
• Any county-to-county flow of fewer than 20 returns. The IRS folds those into “other flows” by region, so a county’s listed origins never add up to its total arrivals. Each profile states how much of the total its listed flows cover.
• Totals the IRS withheld for confidentiality. Of the 3,143 counties in the 2022–23 files, 395 have at least one total withheld because it fell under the 20-return threshold. Those counties have no tracer entry or profile of their own, but they still appear as partners of other counties.

The address on a return is a mailing address, so a post office box or a tax preparer’s address can place a household in the wrong county. Moves to and from Puerto Rico, US territories, military post addresses and other countries are counted as foreign moves.

The site’s own measures

• Net returns: returns that moved in minus returns that moved out, including foreign moves.
• Net migration rate: net returns per 1,000 returns filed in the county in the first year. That base is the non-migrant returns plus the returns that moved out.
• Turnover: arrivals plus departures as a share of the same base.
• Out-of-state share: arrivals from another state as a share of all arrivals.
• Median move distance: the straight-line distance between county centers (from the Census Bureau’s 2023 Gazetteer), weighted by returns, at which half of the listed arrivals came from closer and half from farther. Only listed flows of 20 or more returns are included.
• Average income per return: a group’s total AGI divided by its number of returns, for arrivals, departures and non-migrants. A mean, not a median.
• State-level net rate: net returns from moves between states per 1,000 returns filed in the state in the first year; moves between counties of the same state do not count.

Which counties get a profile

Of 2,748 counties with complete totals, the 285 with at least 40 listed origin counties and 40 listed destination counties have a full profile. Ranks such as “the 3rd-highest” always refer to those 285 counties unless the sentence names another group, for example all counties of one state. The other counties can be looked up in the county tracer.

How to read a county profile

The opening sentence gives the totals. The two maps split the largest flows into those within 150 miles and those farther away; blue lines arrive at the county, orange lines leave it, and a thicker line means more returns. The short paragraph under the maps lists the facts that set the county apart, such as a top-ten rank or a record within its state. Below come the biggest two-way exchanges, the full list of listed origins and destinations, the states involved, four filing years and the incomes reported by each group.

Sources

Source: IRS Statistics of Income Division, SOI Tax Stats – Migration Data (county-to-county and state-to-state files, 2019–2020 through 2022–2023). County locations: U.S. Census Bureau, 2023 Gazetteer Files. IRS migration data: irs.gov/statistics/soi-tax-stats-migration-data. As works of the US government, both sources are in the public domain. Data retrieved 2026-10-28.