Actually, if you read the references by the economists that I cite, in most situations the developers want to maximize profits which means building for higher d

Actually, if you read the references by the economists that I cite, in most situations the developers want to maximize profits which means building for higher density. In much of Manhattan, for example, there are many areas with low 6 story brownstones that could be replaced by higher towers, but the zoning laws don't permit this. In London, where I have lived for about 6 months altogether and in the American cities I mention, the issue is bad use of land because of poor zoning codes. I lack the experience to comment on the situation that you mention relating to Catalan.