We know very lit­tle about com­plex finan­cial sys­tems and how sys­temic risk, as it’s called, is com­put­ed and how you would man­age poli­cies. And if you look back at the finan­cial cri­sis, you can either say, as many econ­o­mists do, ​“It all had to do with badly-designed rules,” which may be part of the sto­ry; it’s cer­tain­ly part of the sto­ry. Or it may have to do with the inter­ac­tion of those rules and human nature, like mort­gage bro­ker greed, opti­mism… And you see it not just in indi­vid­u­als who now have hous­es and fore­clo­sure, but at the high­est levels.