New Upshot Tool Provides Historical Look at Migration

August 14, 2014

An interesting new interactive tool produced by the New York Times’ Upshot blog presents data showing state populations back to 1900, and what share of them were born in-state, abroad, or in other states. It’s a fascinating graphic to look at, but can be hard to interpret. What does it mean that North Carolina’s born-in-state share has fallen dramatically over the last few decades? How should we interpret New York’s remarkably small amount of domestic in-migrants? What conclusions can we draw from California’s declining number of interstate migrants?

The Upshot offers some commentary, suggesting that the rising share of domestic migrants in the south may help boost Democrats’ political fortunes in those states. Looking at New York specifically, they chart how large amounts of the population have gone to Florida. Hopefully, they’ll keep offering more data and commentary along these lines, helping translate a rich dataset for public use.

One point that is hard to ignore when scrolling through the 50 charts is just how big interstate migration really is. As the Upshot makes clear, interstate migration is a major force in America today. While the annual population of migrants may just be between 1 and 3 percent of the population, these annual flows, when repeated year after year, result in huge demographic consequences for states.

Furthermore, this new data can tell a striking story for readers who know the historical tax policies of the various states. Just to focus on one example, California saw rising migration from other states from 1910 to 1960. Then from 1970 to the present day, it has experienced persistent out-migration. No doubt many factors, including the interstate highway system, the Great Depression, agricultural modernization, the invention of air conditioning, an aging population, and others impact these changes.

But it’s also true that California’s Governor Earl Warren cut top income tax rates from 15 to 6 percent in 1943. Income tax rates did not rise above 7 percent until 1967, meaning that California did not have a very high income tax compared to other states at the time. Since the tax hikes in 1967, California income taxes have remained higher than the national average. The 1960s also saw California’s sales tax rates rise well above those of other states, when they had previously been closer to the national average. Eventually, as property taxes also rose rapidly, California citizens became deeply disgruntled with the state’s tax policies. This led to the 1978 “tax revolt” and Proposition 13, which capped and cut property taxes. It is no great surprise that the same rising tax burdens that led to a massive political upheaval were also associated with a reversal in migration patterns.

Taxes cannot be wholly blamed for the ongoing exodus of California residents, but they can play a part (certainly other commonly-cited reasons like job opportunities or weather can’t be blamed). Furthermore (and contrary to some of the Upshot’s commentary), migration of disgruntled Californians (or New Englanders) to southern states may not be good news for southern Democrats. If migrants are leaving behind frustration about taxes, restrictive zoning regulations, or lack of job opportunities, they may not be very likely Democratic voters. Migrants may not be representative of normal Californians or New Yorkers: they may be disproportionately likely to want something else. Exactly how great a role interstate migrants play in shifting partisan voting patterns is not immediately obvious.

But the new tools and commentary from the Upshot clearly show that migration is a major demographic force, and thus economically significant enough to merit attention from policymakers. Prominent changes in the data suggest that taxes may have a role in affecting migration, though certainly taxes are just one of many important variables, and probably not even the biggest factor. As always, talking about migration isn’t simple: migration data is challenging to measure and represent, and even more difficult to interpret.

Read more about migration here.

Check out our interactive migration data here.

Read more on California here.

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