Thursday, March 1, 2012

SEMCOG's Best Guesstimate

The Southeast Michigan Council of Governments (SEMCOG) is tasked with projecting population and employment changes over the next three decades. They do this every four years to help area transportation, environment, and land use planners. Sometimes they come out with pretty curious results.

To help with this task, demographer Xuan Liu uses a widely known modelling package, "UrbanSim" (the planning tool, not the battle game!). Though the software is well respected, its complexity and the need for well-crafted assumptions and data to be fed into it makes some of its predictions a bit puzzling.

Here are some results the piqued my curiosity. When asked about similar seeming anomalies at a recent WATS meeting, Xuan's answer was a shrug, a sheepish smile, and a confession that he often can't fathom what goes on in the software. Anybody have any theories? (In case it helps you to know: UrbanSim uses Monte Carlo methods and Bayesian melding...)

  • Starting with the apparently trivial, Barton Hills, the elite little village north of Ann Arbor, is forecast to lose 17 people while generating 19 new jobs by the year 2020. Really?
  • Dexter is modelled as losing 420 people and 37 jobs by 2020, despite growing 40.8% between 2000 and 2009, according to How come?
  • The City of Ypsilanti is forecast to lose 2,274 people, while Superior Township, immediately to the north, is expected to gain almost the same number: 2,168. Are they expected to move out of Ypsilanti, in spite of Superior's low-growth land policy? Does SEMCOG think the City will pass an income tax that chases people away? Curiously, Ypsilanti is expected to gain 1,035 jobs. Those are not detailed by industry, so what sector is expected to bless the Ypsi with jobs? Meanwhile, state law forbids SEMCOG from revealing Superior Township's job growth potential because of its relatively small number of employers. (St. Joseph Mercy Health Center and its nearby medical clinics are undoubtedly the largest, with the Kia/Hyundai research center a distant second. There really aren't many more!)
  • And finally, Ann Arbor: In spite of its pro-growth policy and having more active building projects than any other part of the county (or of the state?) is modelled to grow by only 433 people to 113,934 in the next decade. Meanwhile, employment is expected to surge by 5,494 to 121,289 jobs. That's more jobs than residents. If the prediction is anywhere near correct, we'll need to beef up the transportation infrastructure or face mega-congestion. (You knew I'd end up saying something like that, didn't you?)

SEMCOG has officially closed its comment period on these draft projections, but if you're really concered about any of these numbers, drop them a line:

To learn more:

1 comment:

  1. SEMCOG also seems to view promoting sprawl & the interests of the townships over as core parts of its mission, which helps explain these puzzling projections as well.