There is a correlation between incomes and house prices, but not strong enough to make accurate predictions from. We can track median and average incomes all we want, but what good is that data if the people buying homes do not have median or average incomes? Also, as we've seen recently, foreign money can be a fairly large part of total demand, and is not covered by income data. While I also don't believe in 7% long term growth, we've seen that basing home buying purely on "fundamentals" can leave you disappointed for a very long time.