Consider the differences between Seattle and Vancouver. For an American city, Seattle is very white and disproportionately childless. The city, however, splatters across the horizon, with few high-rises outside the central business district, while Vancouver is relatively compact and its proliferating residential towers reach to the sky. All this despite geography in Seattle that should encourage density!
The Seattle-Vancouver comparison alone should make you doubt the validity of the “white flight” hypothesis. There are other reasons, however, to reject it. Until 1990 none of Canada’s metropolitan areas declined in population — the country didn’t see shifts in economic geography like what turned cities like Buffalo, Detroit, New Orleans, Flint, Akron, Pittsburgh, Dayton, and Syracuse into what they are today. (The 1990s recession changed that, but the places that shrank tended to small, and located in Atlantic Canada or northern Ontario and Quebec.)
More importantly, white flight can’t explain why the nonblack sections of American cities look rather different from their Canadian counterparts. Nor can white flight (by itself) explain why American suburbs strongly resist residential high-rises, whereas Canadian ones (Montreal excepted) take to them with relative zeal. For example, Chicago’s North Side does not look like Toronto, save for a belt along the lake. Nor does Boston’s central and northern urban area — Back Bay, South End, North End, Southie, Brookline, Allston, Brighton, Cambridge, Somerville, Chelsea, Watertown, Arlington, Belmont, Charlestown, and East Boston — look much like East York or Scarborough. It is true, of course, that the great American ghetto is an American phenomenon, created by America’s strange racial caste system, but racial tensions don’t explain why Houston looks very different from Calgary.
Explanations which rest on more extensive highway systems, he judges, miss the point; Toronto's population is as dense as Los Angeles'. He, and some of his commenters, suggest that the key is to be found in the relative weakness of the Canadian municipality; existing on the sufferage of the provincial government and barely considered separate entities by the federal, zoning regulations may allow for more mixed-use neighbourhoods while--critically--investment in public infrastructure like schools and consistent city-wide or region-wide planning is considerably easier than it would be in the United States.