Are median mortgage payments over, say, 40% (or even 35%) of montly median income? Then, yes.
Also, the annual rent on a house is, taking historical averages, 5% of the median purchase price for the house. Currently, it's about 3.5%.That 1.5% difference is the bubble. I, so typically, find this out after I bought in 2006, at the height of the bubble.
Another nice analysis.