The movie The Big Short is really a pretty good movie. It was closer to the truth than most products out of Hollywood regarding “capitalism.” Plus, it gives the audience at least some idea of what Mortgage Backed Securities (MBS), Collateralized Debt Obligations (CDO), and Swaps are.
The two main things it leaves out—and both are critical for understanding the housing bubble/financial crisis—are the roles that regulation and the Federal Reserve played. Government regulations linked bank capital requirements to the risk of bank assets. This gave banks the incentive to sell their lower rated mortgages and to buy the supposedly highest rated MBS because they could hold more than twice the interest earning assets on their books with the same amount of capital. Additionally, the government required that such assets be rated by the biggest asset ranking firms, effectively giving them oligopoly power. They also left out government agencies such as the Federal Reserve which was flooding the market with credit and Fannie Mae which was gobbling up mortgages to be put in MBSs and CDOs. To be fair, they did momentarily show Ben Bernanke trying to cover up the mess the Fed had caused by “restoring confidence.”
