Frequently Asked Questions about the Tax Foundation Migration Tool

1. Where do your numbers come from?
All of the data on this site comes from the Internal Revenue Service (IRS) and its Statistics of Income division. The raw data is available here.

2. What do the various columns mean?
The migration data was compiled by the IRS using tax returns from each year, based on social security numbers. The "returns" column shows you the number of returns that have moved from one state to another between tax years - for example, if someone filed his or her taxes in Colorado in 1993, and, using the same social security number, filed in California in 1994, that tax return would be counted as a move from Colorado to California for 1993 to 94.

Because individual returns include dependent children, and married couples typically file one single joint return, this number does not reflect total population movement, which is more accurately represented by the "exemptions" column. The number of exemptions on a tax return corresponds with the number of people the return is for; for example, a return for a married couple with two children would have four exemptions. Therefore, this number is closely correlated with the movement of individual persons.

Finally, "AGI" stands for "Adjusted Gross Income" - this is the income reported on the tax return that is the baseline for most tax calculations, and is usually the same as total income. The AGI figures are in thousands of dollars, so a figure of $1,200 between two states would mean that migrants that year had a collective income of $1,200,000.

3. Did you make any manipulations to the data?
No, except for the option to adjust AGI figures for inflation. The numbers came straight from the IRS. In those rare instances in which the IRS, for disclosure purposes, did not include a state-to-state figure, we assumed a value of zero.

4. Why did you create this tool?
Every day, the Tax Foundation uses data from governmental agencies like the Census Bureau, IRS, and others to better inform citizens. Given our specialty and familiarity with IRS data combined with the amount of requests that we receive for information pertaining to migration, we felt it was worth creating this tool as part of our interactive data project.

5. Since you are the Tax Foundation, aren't you trying to imply that taxes are why people move between states?
No. Taxes are one of hundreds of factors that go into a person's decision to move. Others include age, technology, job prospects and the quality/quantity of government services provided. If one looks anecdotally at the data, he/she will see that people move from high-tax states to low-tax states and vice versa. A true study that sought to quantify the importance of taxes for locational decisions would need to account for as many other factors as possible, in addition to possible serial correlation issues between variables, especially taxes.

6. What about foreign inflows and outflows?
We have excluded these from this data set. This tool only provides information related to interstate migration. For information on foreign migration, visit the IRS migration page.

7. The Census Bureau says my state grew in population yet your tool shows people leaving my state. How can this be?
Interstate migration is not the only factor that affects state population growth. Foreign migration, new births, and deaths must also be considered to get a complete picture of a state's population change, and our tool does not include that data.