The article explained some an interesting correlation. Now, the question is are there other factors that weren't considered that could explain the difference in development patterns between two similarly sized metro's like Vancouver and St. Louis?

How much did race tensions play a factor?

What about each of the gov't economic/trade/corporate policies over the 40 years illustrated. Did US differ dramatically from Canada?

Is it possible that the development of the US cities differs dramatically from Canadian and European Cities almost exclusively because of the principals the USA was founded on?