Put a hard cap of no more than 4 percent of GDP; or roughly $570 billion in assets today for financial institutions.

A hard cap on size for financial institutions too big to fail: the percentage should be low enough that banks below that threshold can be allowed to fail without entailing serious risk to the financial system. This limit should be no more than 4 percent of GDP; or roughly $570 billion in assets today. US banks could choose to operate globally or only in the into United States but in either case the size limit would be set relative to the US economy, and offshore activities would count toward the limit. Existing mega banks would have to break themselves up in a way that maximizes value to their shareholders; the resulting smaller institutions would be free to compete fiercely for customers and profits.