Even a look at current population densities destroys this argument as cities like San Francisco need far more density from this sort of inner ring. Keep in mind

Even a look at current population densities destroys this argument as cities like San Francisco need far more density from this sort of inner ring. Keep in mind the actual core in this model is only 25 square miles so even if the core of San Francisco has 20 times the density of the suburbs it fits only 500,000 people. Your 5-15 mile ring fits only 600,000 people so you’ve gone 15 miles out from the centre of San Francisco and you’ve only fit 1,100,000 or so people of the 1.8 million that live in SF proper to say nothing of any of the people living in nearby cities or suburbs you’ve also hit.