BANKS aren’t always popular even in the best of times, but the anger of recent years is unprecedented. The anger, while understandable, has fueled the misguided idea that we should break up the nation’s largest banks.

The argument is simple and sound-bite ready: In the years before the crisis, greedy bankers used their political muscle to grow from small, specialized banks into giant, all-purpose financial institutions. This transformation led to the financial crisis because banks became too big to manage and too big to fail. If we break them back up, we will eliminate the risk of future crises.

The problem is that every part of this argument is based on a fallacy.

The first fallacy is that the emergence of large, universal banks — combining commercial banking with investment banking — was an artificial or unnatural development. In 1990, there were 15,000 banks in the United States; this fragmented market meant that banks could not achieve economies of scale or easily serve clients on a national or global level.

The consolidation that took place was driven by the market’s needs and represented an evolution toward greater efficiency in banking, just as companies like Amazon, Starbucks and Home Depot brought efficiency to retail. Even now, the American financial services industry is far less consolidated than its peers across most of the developed world.