The cause of this crisis is a change in the structure of financial markets which allowed hedge fund operators and other sharks to leverage bad loans geometrically. Republicans as well as Democrats supported this system and gave it legislative backing. You could look on the economic collapse as a convergence of socialist and free market (anti-regulatory) ideological manias. Phil Gramm's deregulatory prejudices are at least as responsible for this economic ruin as Barney Frank's ignorant redistributionist fantasies. No one's hands are clean.
Horowitz then quotes excerpts from an interview with Bill Janeway that provides evidence not merely for the role that dereguation played in the fiasco, but also mathematical economics:
It took two generations of the best and the brightest who were mathematically quick and decided to address themselves to the issues of capital markets. They made it possible to create the greatest mountain of leverage that the world has ever seen….It was a kind of religious movement, a willed suspension of disbelief. If we say that the assumptions necessary to produce the mathematical models hold in the real world, namely that markets are efficient and complete, that agents are rational, that agents have access to all of the available data, and that they all share the same model for transforming that data into actionable information, and finally that this entire model is true, then at the end of the day, leverage should be infinite.
Here was the theory. But banking and financial regulations made it impossible to put it into practice. So what was done about it? Academic economists appealed to Washington to have the regulations removed:
Milton Friedman was prevailed upon to write a letter to Secretary of the Treasury Nicholas Brady, Reagan’s Secretary of the Treasury, as a result of which the Chicago Board was cleared to trade stock index futures, all cash settlement. There is another story in which Alan Blinder on the Democratic side played a similar role, by providing the academic legitimacy for the markets and for the integration into the fabric of finance of the derivatives that instrumented modern financial theory. That enabling role … created a tool through which you could price things that did not heretofore trade. Puts and calls did not trade.
In brief, what happened is that these new financial tools, brought into being through the obtuse cleverness of econometrics, enabled the free market to generate a nearly infinite supply of credit. The so-called “funny money” that free market ideologues wish to blame the Fed for was largely created by the free market! Government regulation had nothing to do with it. On the contrary, it was the absence of government regulation that allowed these non-banking financial institutions to go create a massive credit bubble in the nineties, thereby driving up the Stock Market to five times its value in twelves years.