New Insights into South Dakota’s Population Change

David Sorenson - April 12, 2024
New Insights into South Dakota’s Population Change

Domestic Migration

Domestic migration is a key driver of population growth in South Dakota. As noted in last spring’s article on population change, South Dakota has largely experience positive and increasing net domestic migration, indicating relative “success” in drawing more residents than it loses.

The prior analysis used annual net migration data from the U.S. Census Bureau included in its annual population estimation program. This report uses the primary input to that net migration series to provide a more in-depth look at both in- and outmigration flows for South Dakota. Flows between South Dakota and individual states are also examined.

Summary South Dakota Migration Statistics and Comparison to Other States

The Internal Revenue Service (IRS) annually matches tax returns by social security number and examines location to compute migration between years. The Census Bureau supplements this data for selected groups, for example, those in group quarters and the elderly, in computing its estimates. The IRS also makes a limited version of its data available in its Statistics of Income series.

Matched returns identify those who have moved between states (domestic migration), those who have moved between the US and other countries (foreign migration), those who have moved within a state, and those who have remained in the same country. The most recent data, for 2020-2021, are summarized for South Dakota in Table 1. In addition to returns, the IRS tabulates exemptions on the returns, which are interpreted as the migration flows, and the adjusted gross income (AGI) total for the returns. The AGI has been converted from thousands of dollars to millions for easier presentation, and net migration figures and totals across migration designations have been computed. The total of domestic, international, in-state, and non-migrant values for the outmigration categories is used for the computation of rates. The total of about 750,000 is below the state’s population, reflecting the fact that the IRS database does not capture all individuals and families.

The IRS data indicate that South Dakota gained more than 29,000 residents through domestic inmigration between 2020 and 2021 and lost about 23,000 to outmigration. A similar amount moved among the counties in South Dakota, while the vast majority did not relocate from their county of residence. The domestic migration exchanges netted South Dakota about 6,300 new residents and 450 million dollars in additional income.

South Dakota’s migration experience is better evaluated in percentage terms and compared to other states. Migration counts and percentages for South Dakota and its bordering states is provided in Table 2. South Dakota’s outmigration flow was similar in magnitude to those of the other lower-population states of Montana, North Dakota, and Wyoming, while Iowa, Minnesota, and Nebraska had larger flows, each of them amounting to between 2 and 3 per cent of the state’s 2020 population. South Dakota (3.1%) and Montana (3.3%) had similar higher outmigration rates, while North Dakota and Wyoming approached 5 percent outmigration rates.

The Dakotas and Wyoming had comparable inmigration amounts, but Montana had a distinctly higher inflow. Montana and Wyoming both had inmigration rates of about five percent, while South Dakota and North Dakota had inmigration rates of four and 3.6 percent, respectively. Iowa and Nebraska had modest inmigration rates of 2.4 percent, while Minnesota’s inmigration rate was a low 1.7 percent. When the in- and outmigration flows are combined to calculate net migration, we find that only three of the region’s states experienced positive net migration. South Dakota’s net migration amounted to 0.8 percent of population, while Montana’s was more than double that at 1.7 percent and Wyoming’s rate was about half of South Dakota’s. Iowa’s net loss of just over one thousand residents was less than one-tenth of one percent, while Minnesota’s 16,000 resident loss and Nebraska’s 4,000 resident loss were -0.3 and -0.2 percent, respectively.

The experiences of the region and its states are also interesting when compared to the figures for all states. Figure 1, with outmigration numbers for all states, illustrates the relatively low numbers of outmigrants from most of the region’s relatively low-population states. Figure 2, with outmigration rates, reveals that South Dakota had a fairly typical experience, while North Dakota and Wyoming stand out with their high rates.

Inmigration rates are shown in Figure 3. South Dakota’s rate is again a typical one, while Wyoming and Montana stand out as states with higher rates. Net migration rates, shown in Figure 4, reveal that South Dakota is among fourteen states with fairly high net migration rates, while Montana falls into the top group with Idaha, Florida, and South Carolina. North Dakota is among a group of eight states with low rates, including the populous state of California, New York, and Illinois.

South Dakota Flows to Individual States

While the overall migration numbers and rates provide a useful perspective on South Dakota’s migration, migration exchanges with individual states give a better view of relative attractiveness. South Dakota’s migration flows with the fourteen states which exchanged (inmigration plus outmigration) more than one-thousand residents are shown in Table 3. The list generally follows a ‘gravity model’ pattern whereby the largest flows reflect both proximity and the population of the other state. Minnesota has the largest exchange by far, followed by a group including Iowa, California, Nebraska, and Colorado. Texas, Arizona, and Florida are found in the next group along with North Dakota.

The inmigration and outmigration flows are similar for several states, yielding modest net migration flows. However, sizeable imbalance in flows to and from South Dakota is found for several states. California has a net deficit of over 1500 with South Dakota, while Minnesota and Colorado have net deficits of over 900 and Washington’s deficit is over 600. The largest negative net migration for South Dakota is with Florida at a value of 385, which is much lower than the largest positive net migration flows. The balance is also captured in the calculated inmigrants/outmigrant statistic. California sends a stunning three inmigrants per outmigrant, while Colorado (1.89), Washington(2.38), and Illinois(1.91) also have high in/out ratios. The 0.69 inmigrants/outmigrants for Florida is the only value below one (excepting the trivial -3 migration deficit with Texas).

Figures 5 through 8 illustrate outmigration, inmigration, net migration, and inmigrants per outmigration for the entire country relative to South Dakota. The regional patterns and flows to and from populous states are apparent. Distinctly low exchanges with New England and several southeastern states are also evident. The net migration map (Figure 7) reveals modest net losses to Oklahoma and Ohio and net gains from Idaho, Nevada, New York, Connecticut, New Jersey, and Virginia. In terms of inmigrants per outmigrant, Oregon, New Jersey, and Connecticut join California and Washington with values over 2. Idaho, Mississippi, and Maryland join several northeastern states in the 1.5 to 2 category. Ohio, Oklahoma, Arkansas, and Alabama join Florida in the lowest (0.5-0.75) category.

South Dakota Flows to Individual States in Earlier Years

The 2020-2021 net migration was exceeded only by the following year’s net migration, as reported in the Census Bureau’s annual estimates. The IRS data is not yet available for the more recent years. It is, however, available historically, and the 2011-2012 and 2017-2018 data was examined to assess volatility in migration, especially relative to other states. As shown in Table 4, 2011-2012 net migration was a little more than half the net migration of 2020-2021. Outmigration was virtually the same as in 2020-2021, but inmigration was substantially lower. In 2017-2018, outmigration was again virtually the same, while inmigration was almost six-thousand lower than in 2020-2021.

There were substantial changes in some individual state-to-state flows among the years. The top exchange states are show in Tables 5 and 6. Net migration with Minnesota in 2011-2012 was less than half of the 906 exchange in the 2020-2021. Outmigration was very similar, but inmigration from Minnesota was about 500 residents lower. In 2017-2018, inmigration was even lower, while outmigration was several hundred higher, reversing the net flow to a negative one. South Dakota migration exchanges with Iowa were more stable: net migration varied between 238 and 412, with little variation in inmigration. Migration exchanges with Nebraska were similarly stable, with almost constant outmigration flows. North Dakota’s migration changes were largely driven by outmigration differences. Net migration moved from -225 in 2011-12 to 80 in 2017-18 to 233 in the most recent year.

Migration exchanges with the other neighboring states are more variable. Both North Dakota and Wyoming had their “best” exchanges in 2011-2012, with net outmigration to North Dakota and virtually zero net migration for Wyomning. The 2017-2018 flows indicate positive net migration to South Dakota but less than the magnitude in 2020-2021. The better showing for North Dakota and Wyoming are presumably due to the energy industry. Montana does not even register among the states with a total exchange (inmigration plus outmigration) of over one thousand in any year. In all three years, both the in- and outmigration flows were between 400 and 500, with small net outmigration from South Dakota in the two earlier years turning in to a small net inmigration in 2020-21.

Among other major migration partners, California and Florida exhibit large swings in migration flows. The 1669 California net inmigration to South Dakota in 2020-2021 is much larger than any other year, driven largely by an inmigration flow about one thousand more than in the earlier years. Outmigration to California fluctuated over a range of about 300 across the three years. The Florida net outmigration in 2020-2021 is roughly the same as the one in 2017-2018. In 2011-2012, however, South Dakota had net inmigration of over 700 residents, the largest net inflow of that year. Both inmigration and outmigration were much larger than in subsequent years. In the cases of both California and Florida, significant flows to and from Pennington and Meade (to a lesser extent) Counties, home of Ellsworth Air Force Base, provide caution in interpreting how much elective migration is taking place.

Conclusion

A possible desire to relocate to South Dakota during and after the Covid pandemic and changes due to the realignment of personnel among military installations have arguably had important impacts in the migration patterns of the last decade. The ups and downs of the energy economy in selected neighboring states have also been influential. The future of migration and its impact on population and the economy depends on the degree to which the recent jump in net inmigration is sustainable. The fluctuations over the past several years suggest that there is no guarantee of favorable continuing patterns, although two consecutive years of relatively high inmigration provide hope of a sustained pattern.