Here's an interesting figure from the Missing Middle Initiative showing the change in population of 0-4 year olds in Southern Ontario between 2016 and 2021:

What this shows is that the population of young children declined in the Greater Toronto Area and in Ottawa, but increased dramatically in areas further out, such as in Lanark County (outside of Ottawa) and Oxford County (between London and Hamilton). If you know what home prices are like in Southern Ontario, then this probably makes intuitive sense to you. Families are, as the old saying goes, "driving until they qualify."

But let's look at the data more closely. What the Missing Middle uncovered was that the metric most highly correlated with the population growth of children under the age of 5 was the increase in the supply of housing with three or more bedrooms. More specifically, though, it was highly correlated with an increase in the number of larger owner-occupied homes. Rental housing did not have the same correlation.

They go on to remind us that correlation is not causation, which is true. But regardless, there's a clear recipe here: If cities want to become more family-friendly, house more young children, and not lose them to exurban areas, then they need to figure out a way to unlock more 3-bedroom homes at price points that more families can afford.

Note: As is typical on this blog, I am using the term home to include all housing types, not just single-family housing. A home is not a housing type. It is simply a place where people, families, and households live permanently. Associating the term home with only single-family housing creates a cultural bias that I believe is suboptimal for cities.