Is the Magic Word "Density", or "Location"?

Blogger Pantograph Trolleypole reads Jeff Zupan and Boris Pushkarev:

"I'm not saying that residential density is ultimately unimportant. But I believe its less important for starting a transit system and more important for growing it. There are lessons on this in previous research works that we tend to ignore."

He quotes Zupan and Pushkarev's book Public Transportation and Land Use Policy::

"Residential density is less important for transit use than residential location, ie proximity to a downtown of substantial size or proximity to a rail transit line. If greater transit use is the goal, it is more important to put housing close to a downtown than make it high density."