These restrictions were put in place in the 1930s by political leaders who had just experienced a terrible financial crisis, and were trying to prevent another. But by 1980 the memory of the Depression had faded. Government, declared Reagan, is the problem, not the solution; the magic of the marketplace must be set free. And so the precautionary rules were scrapped.

Together with looser lending standards for other kinds of consumer credit, this led to a radical change in American behavior.

We weren’t always a nation of big debts and low savings: in the 1970s Americans saved almost 10 percent of their income, slightly more than in the 1960s. It was only after the Reagan deregulation that thrift gradually disappeared from the American way of life, culminating in the near-zero savings rate that prevailed on the eve of the great crisis. Household debt was only 60 percent of income when Reagan took office, about the same as it was during the Kennedy administration. By 2007 it was up to 119 percent.

All this, we were assured, was a good thing: sure, Americans were piling up debt, and they weren’t putting aside any of their income, but their finances looked fine once you took into account the rising values of their houses and their stock portfolios. Oops.

Now, the proximate causes of today’s economic crisis lie in events that took place long after Reagan left office  in the global savings glut created by surpluses in China and elsewhere, and in the giant housing bubble that savings glut helped inflate.

But it was the explosion of debt over the previous quarter-century that made the U.S. economy so vulnerable. Overstretched borrowers were bound to start defaulting in large numbers once the housing bubble burst and unemployment began to rise.

These defaults in turn wreaked havoc with a financial system that  also mainly thanks to Reagan-era deregulation  took on too much risk with too little capital.

There’s plenty of blame to go around these days. But the prime villains behind the mess we’re in were Reagan and his circle of advisers  men who forgot the lessons of America’s last great financial crisis, and condemned the rest of us to repeat it.