Housing Scarcity

I knew that zoning and other restrictions had made possibilities for building housing limited, but tonight I saw an example of just how much that was true. 

This graph, created from data for Los Angeles by Strong Towns, shows how that city's housing capacity was decreased over three decades:

I wonder what the equivalent graph looks like for Saint Paul, where it's illegal to build anything but a single-family house on the vast majority of blocks? And where the change started around the same time, I've been told.

Saint Paul is currently studying whether to allow housing with up to four units on a lot, and other uses up to that kind of density as well. To me, it seems like an obvious thing to do.