> But is there a single principled way to present the data that suggests increasing supply in Austin did not decrease costs?

Building more housing will make housing affordable. That’s not up for debate. The extent to which is what you need to look at. You can’t ignore the effects of net migration trends. My comment mostly wanted to address the parent which arbitrarily picked up data points of 2021 and right now and was comparing Austin and San Francisco. Because those specific points in time are tied to the migration of people between the two cities at a higher rate than usual.