Earlier quoted context omitted.
That's true in the US. In other areas, leaving the city might not be a realistic option. Consider Hong Kong as an (extreme) example, where leaving the city means emigrating to another country with another language etc. (yes, HK is technically a Special Administrative Region of China, but can be considered standalone in this respect). The median apartment price/income ratio here is 18, compared to a US average of 3.9…
I would really like to see similar graphics for Europe, Asia, Australia, and Canada. I don't know where to get the data though, and I don't think I could make such a beautiful visualisation as he did.
http://www.demographia.com/dhi.pdf
The top 10 least affordable with respect to median price/income ratios:
China Hong Kong 18.1
Australia Sydney, NSW, 12.2
Canada Vancouver, BC 11.8
N.Z. Auckland 10.0
U.S. San Jose, CA 9.6
Australia Melbourne, VIC 9.5
U.S. Honolulu, HI 9.4
U.S. Los Angeles, CA 9.3
U.S. San Francisco, CA 9.2
U.K. Bournemouth & Dorset 8.9