The debt bubble, and consequently the real estate/commodities/market bubbles were a long time coming. From 1995 to 2007 consumer credit increased by ~13%/year, w/ no commensurate increase in wages to support this increase. I can't find mortgage info earlier than 2004, but the run-up from then until 2007 at ~10%/year. Public and private debt has increased tremendously, more than doubling over the past decade or so, with the end result being ~10-15 trillion in debt accumulation on top of the ~15 trillion already present in 1997. This was of course exacerbated near the end of the bubble by NINJA loans, a breakdown in the rating of CDOs, and leveraging approaching 30:1 in some cases, and after all this fraud was exposed, there was no where to go but down. After people couldn't continue to put things on plastic and refinance their homes, that source of funding was all but wiped out and the spending that was supporting the market, the real estate bubble, and the commodities bubble wasn't there anymore.