Posted this without much comment a while back, but two thoughts:
1. About one billion square feet is accounted for on this graph (excluding Orange County). Of that, 40% is in Manhattan alone — and that doesn’t count the “just across the river” space. Even if all the lesser cities were added in, perhaps one third or one fourth of all people who work in downtown offices in America do so in Manhattan.
Compare that to the one-half of one percent of Americans who live on Manhattan. That’s either impressive for New Yorkers, dispiriting for those of us who like working downtown but want more choices than just NYC, or a market opportunity for the rest of the country.
2. It’d be better to use a graph of regional office shares to assert this point, but it appears that about 50 million square feet of office can ensure that downtown can assert retail dominance over the region. There are exceptions, of course: DC’s retail center is rather diffuse (some zone between Georgetown, Chevy Chase, and Tyson’s), and Portland has a healthy retail sector despite its relatively small office market. Still, for those looking to build 24-hour downtowns, it seems more efficient to pursue residential rather than office as the complementary use.