Ever since Portland adopted an urban growth boundary (UGB), there have been numerous and very legitimate criticisms of the policy. The boundary has increased housing prices, devalued the properties of certain land owners, and robbed consumers of housing styles they might prefer. But there is one potential negative that has been overlooked - and is rather ironic - given the plan's original intentions. The boundary may be driving suburban sprawl to points well beyond the Portland metro area.

The boundary was first drawn in 1979 by Metro, a 3-county, 24-city regional planning body that helps dictate land-use decisions for the Portland MSA. It was designed to protect farmland, slow sprawl, and encourage urban density, by surrounding Portland and its key suburbs with a preservation ring of large-lot agricultural zoning.

Although the boundary has been expanded 35 times, its total land area, according to ModernFarmer.com, has grown by only 14%, while population has jumped 61%. Therein lies the problem. When the boundary was drawn in 1979, Portland's median home prices were around the national average of $63,000, and the metro remained affordable while suffering through recession and population decline in the 1980s. But the boundary didn't prove so practical once population growth revived. Between 1990 and 2000, metro Portland's median home prices doubled, and they have continued increasing to $358,000, 90% above the national average.

This has prevented many people from living in the metro area - much less within the growth boundary, where prices are much higher. But it appears that, rather than foregoing Portland's job market altogether, they're just leapfrogging to even more remote areas.

Beyond just the statistics, this would be evident to any Metro planner who bothered to notice the lay of the land beyond their 3-county domain. While it is true that when passing many parts of the growth boundary, the land shifts instantly from urbanization to beautiful countryside, a further drive reveals that a lot of the growth is just further extending. For example, 2 of Oregon’s 4 fastest-growing cities are small ones - Sandy and Canby - that sit about 10 miles beyond the growth boundary. Just north of Portland, across the Columbia river and outside the UGB, is Vancouver, which is routinely one of Washington state's fastest-growing cities. Since 1990, its population has nearly quadrupled from 46,000 to  173,000, and it too has fast-growing northern suburbs. And Salem, 60 miles to the south, has shown formidable growth recently also.

Portland's UGB caused leapfrog sprawl and stretched the CSA.

Well, it turns out that a lot of these places are just becoming commuter suburbs for Portland. Average commute times in Sandy, for example, are 29 minutes, suggesting that much of its population drives into the city daily. About 31,000 make this daily trip from Salem. And Vancouver-to-Portland commute times have increased by 300% since 2011, because of all the added people crossing the river. In fact, a 2015 analysis by demographer Wendell Cox found that Portland’s combined statistical area—which embodies the commuter networks emanating from given MSAs--is starting to resemble metros like New York. For example, 15% of resident workers in Benton County, which enshrouds Corvallis, now commute to one of the Portland MSA's 5 main counties, even though it is 85 miles away.

"Perhaps the greatest irony is that an 'urban containment' policy designed to prevent sprawl could well be accelerating it," writes Cox. "Higher prices, in part due to this policy, have forced more people to look ever further for housing that is affordable."

There are two big reasons why this UGB seems to be backfiring. The first is that, after Metro drew the boundary around Portland, the land inside it wasn't sufficiently deregulated. Instead, parochial Nimby battles and anti-density scaremongering means the city, even today, maintains a mostly single-family residential character. This in itself is a severe market distortion, considering that average one-bedroom rents in the city proper are $1,455, and that much of the new development going up is, despite all the regulatory hurdles, much denser than before.

The second is that Metro didn't anticipate how complex the consumer market for sprawl can be as well. Like other major metros, there is likely a large contingent of the 2.4-million-person Portland metro that wants to work in the urbanized area, but doesn't want to live within it, or can't find their preferred housing style there. Their natural settling point, in an open market, might be the undeveloped land most immediately adjacent. But because Portland's UGB limits these areas, this group must settle further out.

Sadly, this outcome exists wherever cities mix tight infill regulations with adjacent suburban growth restraints. For example, much of the developable land on the peninsulas immediately north and south of San Francisco is off-limits due either to preservation policies or Nimbyism in different municipalities. As a result, the region's fastest growth is occurring 40 miles away--in cities like Dublin and Antioch--that require 90-minute rush-hour commutes into San Francisco.

Similar dynamics are occurring in Boulder, which has a preservation ring, and even my home county of Albemarle. The only land within Albemarle that the Comprehensive Plan allows for development is the city of Charlottesville - a small university town with a strong economy - and some surrounding slivers of growth area. The remaining 95% is dedicated to rural preservation. This means Albemarle has median home prices of $306,000, and that much of the workforce makes long commutes in from neighboring counties.

The lesson here - at least for those who think the laws of supply and demand apply to land just like everything else - is that there are consequences to UGB-style policies. And they may not even be the ones that environmental or density advocates want. That is, if bustling cities prevent what can be vaguely defined as "sprawl" on their nearest virgin land, it's not like the people will go away and the sprawl will stop. It may resurface in even more remote places. This is counterproductive both for these advocates, and for the people who must suffer long commutes each day.

[This article was originally published in Forbes.]