Housing Supply vs. Prices

I've been looking for a simple chart demonstrating the connection between housing supply and prices, and how different cities have experienced different rates of growth.  Not finding one I made my own.

This calculates annualized growth in housing units based on the change between the 2000 and 2010 census, and compares that to the price change from Jan 2000 to Jan 2010 based on the S&P/Case-Shiller Index.

This shows 18 of the 20 cities in the S&P Index, excluding Cleveland and Detroit which had negative population growth.  Changes in housing supply don't explain all the variation in price, but they explain a lot of it.

How many households in Portland were earning 47% more in 2010 than they were in 2000?  That's what they'd need to have the same home-buying power over that time. 

It begs the question of what's a bigger driver of gentrification:  A housing policy that encourages construction, pushing the city down and to the right along that curve, or a policy that discourages new construction which leaves housing unchanged but ensures that only an ever wealthier class of people can afford it?