Whenever people who support restrictions on building want to justify the limits of density, they say the area is too dense, or possibly too dense for the present traffic capacity or quality of life. This is true regardless of density. It’s against this background that one should read Kaid Benfield’s article in Grist attacking Ed Glaeser’s proposals for upzoning in Manhattan. Manhattan, we are told, is already the densest county in America, so why build more?

Multiple lines of response come to mind; you should think of them as separately as possible. The first is that Benfield not only makes an argument about Manhattan’s density, but also posts lovely images of landmarked streets in the West Village, which Glaeser wants to permit replacing with 50-story residential towers. In light of that, let us remember what historic districts are, in practice: they are districts where wealthy people own property that they want to prop up the price of. They are designated arbitrarily, make arbitrary rules, and protect clearly non-historic buildings.

The densest neighborhood in Manhattan, the Upper East Side, has about 46,000 people per square kilometer, rising to about 70,000 in the upper-middle-class (as opposed to wealthy) section east of Third Avenue. The West Village only has 26,000, so there’s clearly room to build up.

There is no inherent reason to go by county or borough density rather than by neighborhood density. By the same token, one could say that the Northeast is the densest region in the US and therefore requires no more density. Southern boosters might like this, but not the people reading Grist, who care about environmental protection more. There is no induced demand with people: allowing taller buildings is not going to make more people be born, which means all it does is permit population to shift from exurbs to city centers.

What is more, there already is demand for more housing in Manhattan: last decade Manhattan’s population grew faster than that of the rest of the city as well as the rest of the metro area, amidst skyrocketing rents. In fact the reason I don’t trust the census is that it believes that New York added more housing units than people last decade, at a time of rising household size and stable vacancy.

There are ways to increase Manhattan density without plopping 50-story towers everywhere. For one, even the Upper East Side has few such towers – it is built to about the 20th floor. Unlike with office buildings, which favor more agglomeration, residential buildings remain mid-rise even if higher densities were possible, as they were in the 1920s; today, on the order of 1% of the city’s residential stock is located above the 20th floor. However, any density increase requires a rise in height – from 5 floors to 7 in Harlem and the Village, from 10 to 15 in Morningside Heights, and so on – without the loss of lot coverage coming from project-style towers.