If you click the link and, leaving all the rest of the defaults alone, drop the required affordable housing percentage from 10% to 0%, you lose about 4,000 affordable units but gain 6,000 market-rate ones.
So, would this change increase or decrease displacement?
Well, another recent Berkeley study concluded that a new market-rate apartment has about half the displacement-fighting impact of a below-market-rate apartment: http://www.urbandisplacement.org/sites/default/files/images/...
Therefore, the benefit of the extra market-rate units fails to offset the damage from the loss of affordable units (6000/2 < 4000). It fails similarly, but to a lesser degree, if you drop it to 5%.
But if you crank it up to 15%, the gains from the extra affordable units are overwhelmed by the lost market-rate units (4000/2 > 784). So it looks like the default value of 10% is the sweet spot.
By the way, the math is even easier for the 25% threshold that Supervisors Jane Kim and Aaron Peskin are proposing (http://www.sfchronicle.com/opinion/openforum/article/Prop-C-...), because that would actually lead to less affordable housing being built. Less market-rate, too. A double displacement whammy.
So, would this change increase or decrease displacement?
Well, another recent Berkeley study concluded that a new market-rate apartment has about half the displacement-fighting impact of a below-market-rate apartment: http://www.urbandisplacement.org/sites/default/files/images/...
Therefore, the benefit of the extra market-rate units fails to offset the damage from the loss of affordable units (6000/2 < 4000). It fails similarly, but to a lesser degree, if you drop it to 5%.
But if you crank it up to 15%, the gains from the extra affordable units are overwhelmed by the lost market-rate units (4000/2 > 784). So it looks like the default value of 10% is the sweet spot.
By the way, the math is even easier for the 25% threshold that Supervisors Jane Kim and Aaron Peskin are proposing (http://www.sfchronicle.com/opinion/openforum/article/Prop-C-...), because that would actually lead to less affordable housing being built. Less market-rate, too. A double displacement whammy.