Senator Sanders, in calling for a break-up of our largest banks, is implicitly targeting our four largest banks: JPMorgan Chase, Bank of America, Citigroup and Wells Fargo. All four of these rank among the top 10 in the world, with JPMorgan being No. 1, Bank of America No. 4, Citigroup No. 7 and Wells Fargo No. 8. First of all, it is important to understand that these banks are as large as they are primarily because, in the great financial crisis of 2008-2009, they were required by U.S. banking regulators to absorb a number of other banks and financial institutions that were on the brink of collapse.