I think that was certainly true for the last 30 years but as more things start up further away, some of those things can grow into their own "centers". For example when IBM decided to build a west coast center for Watson they chose 505 Howard in San Francisco over space in San Jose or one of the Peninsula cities. At one time they owned two reasonably sized buildings that corner of El Camino and Page Mill Road in Palo Alto. So they felt that some of the center of gravity had shifted.