“While bank lobbyists and some commentators are suddenly taken with the idea that an active debate is under way about whether to limit bank size in the United States, they are wrong. The debate is over; the decision to cap the size of the largest banks has been made. All that remains is to work out the details.

“To grasp the new reality, think about the Cyprus debacle this month, the Senate budget resolution last week and Ben Bernanke’s revelation that — on too big to fail — “I agree with Elizabeth Warren 100 percent that it’s a real problem.”

“Policy is rarely changed by ideas alone and, in isolation, even stunning events can sometimes have surprisingly little effect. What really moves the needle in terms of consensus among policy makers and the broader public opinion is when events combine with a new understanding of how the world works. Thanks to Senator Sherrod Brown, Democrat of Ohio; Senator Warren, Democrat of Massachusetts, and many other people who have worked hard over the last four years, we are ready to understand what finally defeated the argument that bank size does not matter: Cyprus.”

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Read Simon Johnson’s full Economix blog post here