When David Egan-Robertson was asked to project Wisconsin's population trends 30 years into the future, he went 30 years into the past. Egan-Robertson, a demographer in the CALS-based Applied Population Laboratory, is the author of a report on the state's 30-year population projections issued in July by the state Department of Administration.
“The projections go out for 30 years, so we look at the past 30 years—the number of births and number of deaths and migration pattern in and out of the state,” he says. “The 30-year pattern is especially important in the migration area. Migration traditionally has risen when economy is in good shape, so there there’s a long cyclical pattern. If you looked at just ten years you’d miss a lot.”
The report predicts that by 2040 the state's population will grow by 800,000 people, or about 14 percent, but that growth will be sort of a bell curve. He sees two decades with an increasing growth rate followed by a flattening out in the 2030s. He anticipates that the state will add upwards of 315,000 people in the 2010s, then grow by more than 370,000 in the 2020s, but add only 120,000 in the 2030s. Reasons for the falloff in the third decade: A large share of the Boomer generation will die in that decade, while births will increase only slightly and net migration will ease up after two decades of strong growth.
This isn't Egan-Robertson's first go at this task. He compiled a set of 30-year projections in the mid-2000s when he was working at the DOA's Demographic Services Center (the agency is required by statue to produce state population projections every five years). After he took a job at the Applied Population Lab (a unit of the Department of Community Sociology) last year, DOA opted to contract with APL to have him develop this year's projections.
It's important that he get this right, because the 30-year projections inform some pretty important decisions. “State agencies take the projections and use it in their policy and analysis,” he explains. “It affects workforce projections, social service planning—a lot of high-level state planning functions. A lot of state policy is steered by these projections, based on what needs are going to be.”
And that's just part of it. Now that he's completed the statewide projections—a project that took him about half a year—Egan-Robertson will spend the next six to nine months projecting population trends at the county and municipal level. The local projections have an even larger set of stakeholders—including county service agencies, regional planning commissions, municipalities. “Things like smart- growth planning at the community level are informed by these projections,” he says.
Egan-Robertson is pretty comfortable with his numbers. He compiled the DOA's previous population projection report in the mid-2000s when he worked for that agency in the 2000s, and his projections were about 30,000 above 2010 U.S. census figures for Wisconsin. Thirty thousand out of 5.7 million people isn't bad.
He credits that accuracy to having access to demographic models that were honed over many years through a collaboration by UW-Madison and DOA population researchers— in particular, by Paul Voss, former director of the Applied Population Lab, and Bal Kale, long-time demographer at the Demographic Services Center.
"[Vos and Kale] began collaborating the late 70s and worked together for 35 years developing the methodology,” Egan-Robertson says.