Migration data and what it does not tell you

Migration statistics have become the standard opening slide of every market presentation, and they are genuinely informative — about a narrower thing than they are usually used for.

Where the data comes from

Census Bureau estimates, published annually at county and metro level, covering total population change decomposed into births, deaths, domestic migration and international migration.

The decomposition matters. A metro growing through births has different housing demand from one growing through in-migration of working adults.

IRS county-to-county migration data, derived from tax return filings. It shows flows between specific counties and includes aggregate income of the movers, which is the most useful feature.

Published with a lag of a couple of years, which limits its value for timing.

Postal address change data and various commercial datasets, which are more current and less rigorous.

Moving company reports, which are widely cited and reflect one company's customer base, not the population. Treat them as anecdote.

What the headline number omits

Income of the movers. Ten thousand people arriving with median household incomes of $95,000 generate very different housing demand from ten thousand arriving at $38,000.

The IRS data includes this and almost nobody uses it.

Whether they rent or buy. A metro attracting affluent retirees who purchase outright adds nothing to rental demand and quite a lot to purchase prices.

Household size and composition. Housing demand is driven by household formation, not headcount. Two thousand people arriving as five hundred families need five hundred units. Two thousand arriving as individuals need considerably more.

Where within the metro they go. Metro-level in-migration concentrated in three suburban submarkets tells you nothing useful about the urban core, and vice versa.

The out-migration. Net figures hide gross flows. A metro with high in-migration and high out-migration has a transient population, which means higher turnover — an operational cost — even where the net number looks strong.

The lag problem

All of this data is historical. By the time a migration trend appears in published statistics, is written about, and becomes a market narrative, it has been running for several years.

Which means it is priced. Buying into a market because of a well-publicized migration trend is buying at the price that trend has already produced.

The trend also has to continue for the purchase to work out, and migration patterns reverse. Several markets that saw exceptional in-migration during and immediately after the pandemic period subsequently saw it moderate substantially.

What drives migration, and whether it persists

Understanding the driver tells you whether to expect it to continue.

Employment. The most durable driver, and it depends on whether the job growth itself is durable. Growth concentrated in one industry or one large employer is fragile.

Cost of living, particularly housing. Self-limiting by nature. People move to affordable places, which raises prices, which reduces the affordability advantage. This has visibly happened in several high-growth markets.

Remote work. A genuine structural change whose eventual scale remains uncertain, with return-to-office policies moving in both directions.

Retirement, which is demographically driven and reasonably predictable, and which affects healthcare demand and single-family purchase more than rental.

Climate and disaster exposure, which is beginning to show up in insurance costs and, in some places, in movement. This is early and worth watching, particularly since insurability affects financeability.

The affordability ceiling

The constraint that catches migration-driven markets.

In-migration raises housing costs. At some point, the cost advantage that drove the migration disappears, and the arriving population's incomes cannot support the prices.

The measure to watch is the ratio of median rent to median local income. When it approaches or exceeds thirty percent, rent growth becomes constrained by ability to pay regardless of demand.

And that constraint tends to arrive at the same time as the new supply that the growth attracted.

What to use instead

Employment data at county level, by sector, with concentration analysis.

Wage growth relative to rent growth.

Household formation, not population.

Migration data with income attached, from IRS county flows.

Supply under construction relative to existing stock.

And the actual leasing experience of local property managers, which is more current than any published dataset.

The summary

Migration is one demand input. It is not a thesis.

A market with strong in-migration, heavy new supply and stretched affordability is a worse proposition than one with flat population, no new supply and rents well within local incomes.

The second appears in no presentation, which is part of why it is available.

General information about real estate markets, not investment advice. Demographic trends change and past patterns do not predict future outcomes. Consult qualified professionals about your own circumstances.