2008 was a credit crisis that started in housing, and the securitization chain is what carried it to the whole economy. Lenders packaged huge numbers of mortgages into securities and sliced them into tranches, and the bond-rating agencies rated much of that paper far higher, often triple-A, than the quality of the underlying loans justified. That mispriced rating was the fault line. Pension funds and institutions around the world, well beyond the US, poured money into these securities believing they were safe. When the underlying loans defaulted in large numbers, the damage left housing fast. Credit availability collapsed globally, and major banks were threatened, some surviving only through government intervention. Because the bad risk had been spread worldwide through those securities, a US mortgage problem became a global financial one. The perspective worth keeping today: housing downturns have essentially never coincided with a broad recession except 2007 to 2008, and in that episode housing itself caused the recession. In a more typical recession, housing tends to be relatively insulated rather than the thing dragging everything down. So don't assume every economic slowdown hits home values the way that one did. Each downturn has its own cause, and 2008 was specifically a housing-and-credit event.