While the other poster misunderstood the abatement concept, he gets at an interesting point. I can't find how much taxes in total since the inception of 421a have been abated, but it could be interesting to compare that number and see what could have been done with the money over the years. Would more housing units have been able to be built by the government instead? I.e. if we stopped this abatement and just directly build subsidized housing with the future tax revenue that would have been abated (ideally better than NYCHA, in my dreams...) would we have more or less affordable style housing?