Paul Krugman writes: “And greed — you mark my words — will not only save Teldar Paper, but that other malfunctioning corporation called the U.S.A.”

That’s how the fictional Gordon Gekko finished his famous “Greed is good” speech in the 1987 film “Wall Street.” In the movie, Gekko got his comeuppance. But in real life, Gekkoism triumphed, and policy based on the notion that greed is good is a major reason why income has grown so much more rapidly for the richest 1 percent than for the middle class.

Today, however, let’s focus on the rest of that sentence, which compares America to a corporation. This, too, is an idea that has been widely accepted. And it’s the main plank of Mitt Romney’s case that he should be president: In effect, he is asserting that what we need to fix our ailing economy is someone who has been successful in business.

In so doing, he has, of course, invited close scrutiny of his business career. And it turns out that there is at least a whiff of Gordon Gekko in his time at Bain Capital, a private equity firm; he was a buyer and seller of businesses, often to the detriment of their employees, rather than someone who ran companies for the long haul. (Also, when will he release his tax returns?) Nor has he helped his credibility by making untenable claims about his role as a “job creator.”

But there’s a deeper problem in the whole notion that what this nation needs is a successful businessman as president: America is not, in fact, a corporation. Making good economic policy isn’t at all like maximizing corporate profits. And businessmen — even great businessmen — do not, in general, have any special insights into what it takes to achieve economic recovery.

Why isn’t a national economy like a corporation? For one thing, there’s no simple bottom line. For another, the economy is vastly more complex than even the largest private company.