[ssiguy]

There are many reasons why downtown populations are soaring and here are a few key ones:

First, declining incomes relative to the cost of a house. Housing prices have uniformly risen significantly faster than incomes in the last 40 to 50 years and hence the SFH is not optional for many especially the working class. In very expensive cities like Vancouver, SFH are only for the wealthy.

Second, women entering the workforce. Up until 1980 most women didn't work outside the home and certainly not full-time. They were "home makers" and had the time to maintain the SFH home and now they don't and so want smaller homes that are easier to maintain.

Third, fewer kids. As the family size has shrunk considerably, there is no longer the need or desire to have a big suburban home with a big lot and so apt living {which is overwhelmingly downtown/inner city} is now practical.

Fourth, declining crime rates. Generally crime rates are lower today than they were in the 1970s due, in large part, because of an older population. People are far more likely to commit crime {which was traditionally higher in downtown areas} in the 15 to 35 demographic cohort than those in the 35 to 55 range.

Fifth, better race relations. This is particularly true in the US where living beside a black person no longer scares the white person to flee to the suburbs. White flight is effectively over. This has also not just brought more people downtown but generally higher income ones and the political power that comes with leading to better urban amenities and a more pleasant urban realm.