I certainly don't know. And neither does anyone else--it's just too complicated of a system for any human mind to grasp in full. But Russell Roberts and Arnold Kling have has good of an idea as anybody, so this discussion between the two of them is well worth watching:
Russ and Arnold trade economic origin stories... Perils of Econ 101... The past decade as a massive misallocation of resources... Why Ben Bernanke might be the worst man for the job... Is the government making the crisis even worse?... A call for humility in economic prognostication...