It’s not really a demand function, as there is already massive demand in DC for everything. Given a scarcity of housing, where you can fill up anything you build, it’s driven by margins for profit optimization. Profit for developers here means maximizing the price of condos or rents. Making condos more affordable via tax incentives and whatnot doesn’t actually change anything for the developers unless it means they can raise prices to increase profit. So now you’re cutting tax revenue to boost developer profits by roughly the same amount, and cost of condo units has gone up.

And you certainly could require condo or coops to be built, but I’m not convinced that’s what people want. There might be data saying it is, but Im not seeing it. Certainly not enough for the city zoning boards to pick and choose where they implement those requirements.

Best solution is to build build build as much as possible. Supply goes up and meets demand, prices come down (or at least level off) and condo vs apartment economics can reach a more natural equilibrium.