Building on yesterday's post about inclusionary zoning, below is a telling diagram from the Urban Land Institute showing which areas of Portland can support new development and which areas cannot. To create this map, ULI looked at achievable rents in each US census block to determine, quite simply, where rents will cover the cost of new development (all types of construction).

However, in their models they are also assuming a land value of $0. And typically people want you to pay them money when you buy their land. So in all likelihood, this map is overstating the amount of blue -- that being land where new development is feasible.

But it does tell you something about developer margins. A lot of people seem to assume that the margins on new developments are so great that things like inclusionary zoning can simply be "absorbed" without impacting overall feasibility. The reality is that there are large swaths in most cities where development is never going to happen even if you were to start handing out free land.

This map is also helpful at illustrating some of the impacts of IZ. If you assume that rents are the highest in the center of the city and that they fall off as you move outward, then the outer edge of the above blue area is going to be where development is only marginally feasible. And so any new cost imposed on development would naturally start to uniformly eat away at the blue feasible area -- that is, until rents rise enough to offset it.

Of course, this is a simplified mapping. Land usually costs money. Land values might also be highest in the center and fall off as you move outward, or there could be pockets of high-cost land. There may be more price elasticity in certain sub-markets compared to others. So the impacts of a new development cost may not play out as neatly as I outlined above.

Regardless, there will be impacts, which is why I find this map telling even if it isn't fully accurate or up to date. Maybe some of you will as well.