Simon Johnson writes: Nearly seven years after the global financial crisis erupted, and more than five years after the passage of the Dodd-Frank financial-reform legislation in the United States, the cause of the crisis – the existence of banks that are “too big to fail” – has yet to be uprooted. As long as that remains the case, another disaster is only a matter of time.

The term “too big to fail” dates back several decades, but it entered wide usage in the aftermath of the collapse of Lehman Brothers in September 2008. As problems spread throughout the financial system, the US authorities decided that some banks and other financial companies were so large relative to the economy that they were “systemically important” and could not be allowed to go bankrupt. Lehman failed, but AIG, Goldman Sachs, Morgan Stanley, Citigroup, Bank of America, and others were all rescued through various forms of massive – and unprecedented – government support.

The official line at the time was “never again,” which made sense in political and economic terms. These large financial firms were provided a scale of assistance that was not generally available to the nonfinancial corporate sector – and certainly not to families who found that the value of their assets (their homes) was below the value of their liabilities (their mortgages).

If large, complex financial institutions continue to have an implicit government guarantee, many people – on both the right and the left – would agree that this is both unfair to other parts of the private sector and an inducement for big banks to engage again in excessive risk-taking. In the jargon of economics, this is “moral hazard.” But no special training is needed to know that it is unwise and dangerous when bank executives get the upside (huge bonuses) when things go well and everyone else bears the downside risks (bailouts and recession).   Regulate Banks for Success