We have glimpsed a vision of Dallas' future, and it is bleak. By 2050, according to the Dallas Business Journal's read of new data from the Texas Office of the State Demographer, Collin County will have ballooned to 3.8 million people. Dallas County, once upon a time the "urb" in Collin County's "suburb," will have a population of just 3.5 million. The inversion of the city-suburb dynamic will be complete. Frisco -- or maybe Anna -- will supplant Dallas as the area's dominant municipal force, propelling the North Texas region to unprecedented levels of prosperity that is nevertheless insufficient to fix Dallas' pot holes.

But must this be so? Is Collin County's population really going to quadruple over the next 35 years? The answer is, probably not. While the DBJ imbues the population projections with the aura of prophecy, State Demographer Lloyd Potter does not.

"For that scenario, we have migration rates from the last decade from 2000 to 2010 [and] simply keep those rates constant over the projection period," Potter explains. "Essentially what it shows in the projection is that this is what Texas will look like in the future if the growth rate looks like it did between 2000 and 2010."

Because Collin County's growth rate between 2000 and 2010 was high, so, too, is it's projected growth over the next 35 years. Dallas, by contrast, grew relatively slowly during that decade and so is projected to keep growing slowly through 2050. This is basically just taking a trend line on a graph and extending it.

The problem with this approach is that it's probably not going to produce very accurate predictions. It will probably do a pretty good job of projecting out five or 10 years, Potter says, but "if you go out much more than that you start to be on less firm ground." At some point, growth is probably going to slow.

Then again, this approach isn't supposed to produce accurate predictions. It's more of a growth ceiling, as Potter and his colleagues note in an explanation of their methodology: "Because growth was so extensive during the 2000-2010 decade it is likely to be unsustainable over time and thus this scenario is presented here as a high growth alternative."

Where there's a ceiling there's also a floor, in this case projections that assume that no one will move into or out of any Texas counties, whose populations will fluctuate based only on the predicted ratio of births to deaths. In this scenario, Dallas County actually grows about three times as quickly as Collin, mainly because Dallas has a much larger population of Latinos, who on average have more children. But this scenario isn't realistic either.

Growth in Collin and Dallas counties, and in the rest of Texas, will almost certainly be somewhere in between the floor and the ceiling, which is why Potter and his colleagues offer another projection, a third way. It's not quite as simple as adding floor and ceiling and dividing by two, since it takes into account variations in migration and mortality among various subgroups of the population (e.g. age, gender, and ethnicity), but it's basically in the middle. In that projection, Collin County winds up with a population of about 1.8 million by 2050, more than twice the 782,341 people it had in 2010 but still far less than Dallas County's projected 3.3 million.

Even those figures shouldn't be taken as gospel. Collin County still has plenty of room to grow and, with no signs of an economic slowdown on the horizon, it might wind up closer to the ceiling than the floor, Potter says. And he and his colleagues don't even try to adjust for anything that might happen between now and 2050 to influence population patterns: government policies, climate change, economic collapse, the rapture, etc. These are population projections. "When people start doing that," Potter says, "they call them forecasts."

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