Have you ever got a mortgage for your house? The most strict guideline was 28% of your pre-tax income. For a family with 55K annual income, that is to say $15,400 annually can be used to pay for mortgage. Far more than the $600 the author quoted.
The federal government actually did too little for the housing market, and too late. That's why so many folks here could get 10-20% returns on their investment.
As long as the high return is here, capital will come to chase the return. Once the irregular forces (foreclosures, short sales) in the market subsides, the 10-20% annual return will become 6-10% annual return. That is to say, average price will go up by around 50% once foreclosure/pre-foreclosure activities go back to a normal range. I do not have the crystal ball that the author has, so not sure whether it will take 5, 10 or 15 years. My guess is it will be between 5 and 10 years.
This so called "公认的安全（可持续性发展）界限90%" is not substantiated. Nobody in the US has the urge to "达标". This reduction is simply the result of banking sector becoming more risk averse.
This debt level is more likely to go up than going down, as the banks starts to lend again.
This author compiled a lot of data.
All his data supports his conclusion.
He already knew his conclusion before he collected any of his data.
I had the pleasure of reading a lot of similar articles arguing why the US housing market would never crash. Full of data and graphs. That was 2005-2006.
我刚买了一块地，就在我租住的公寓附近，先种花种树，全当是学习南泥湾精神，实践南泥湾理想；一边等着美国房价跌、跌、跌！跌到不能再跌的2015年初，再出手买最理想的房子吧！
搜集提供这么多信息资料实在是很辛苦，向你致敬并祝你一切顺利！