­JPMorgan Chase, the nation’s largest bank, has shrunk since 2014, but it entered 2016 with 50 percent more assets than it had in 2007, in great part because of its acquisition (on the cheap) of Bear Stearns and Washington Mutual in 2008. Early this spring, the top banking regulators announced that because of their size and complexity, five of the eight largest banks, including JPMorgan, still didn’t have workable plans to avoid going out of business without taking the economy down with them — suggesting that they would probably need to be bailed out if they began to collapse again.

So are they headed toward failure? To judge the likelihood of that, the first thing to consider is what types of risk they’re taking on. And on that front, at least, the changes have been far more notable than most Americans realize. For starters, Dodd-Frank’s “Volcker Rule” forced the banks to get rid of the trading desks where they made enormous speculative bets for their own profit. There was some talk that the banks would find a way around the rule, but almost every bank has disbanded these trading teams or sold them to hedge funds. And this is just one of the risky businesses that the big banks have jettisoned in recent years. The most risky — and profitable — units at all the banks before the crisis were the so-­called fixed-­income divisions, where the banks created and traded bonds and derivatives. In 2006, these departments were the single largest sources of revenue at banks like Goldman Sachs and Morgan Stanley. Today, by contrast, the amount of money the big banks make from their fixed-­income divisions is less than half of what it was at the peak in 2009, and it continues to fall.

There are multiple reasons for this evolution, including global economic shocks like the Greek debt crisis and the new trading rules in Dodd-Frank. But the greatest engine of change has been some rather arcane accounting rules, known as capital requirements, set by the central banks of governments around the world. Put most simply, capital requirements force banks to raise a specific amount of money (usually from investors) for every dollar they lend or trade. In 2010, central banks agreed that the large commercial banks needed to double or even triple their capital buffers. Riskier ventures require even more capital.

The most immediate impact of these rules has been to serve as a sort of brake on business activity, given the hassle and cost of raising more capital. And indeed, when banks today explain why they are moving into or abandoning certain businesses, they almost always cite capital requirements as their main motivation. The Federal Reserve official in charge of these regulations, Daniel Tarullo, was recently called “the most powerful man in banking” by The Wall Street Journal. Tarullo is now pushing to raise the capital requirements even higher for the very largest banks, like JPMorgan and Citigroup, and there are signs that this could do what Bernie Sanders could not: force the biggest banks to split themselves up.