> Give this pool of workers a big enough carrot, maybe its a fitness center or a pool or some astroturf for the dog, and they will gladly move out of that 50 ye

> Give this pool of workers a big enough carrot, maybe its a fitness center or a pool or some astroturf for the dog, and they will gladly move out of that 50 year old dingbat and into this new construction This is only partially true though. What you mean is some percentage of people will move into the new construction. But of course, some people will see that the unit they live in is becoming more affordable and decide that they would like to take advantage of relatively lower rent. Over time and on average you are correct - that building nice new homes will relieve pressure on somewhat less nice older ones, but it will take time. Also, we aren't talking about mandating affordable units, which is a thing in some places, but rather a developer trying to apply for subsidies for building affordable units. I totally agree that we should not put up barriers to building market rate units, but it's also worthwhile to incentivize some artificially low cost units as well to help solve the problem for some people today instead of 10 years from now.