First, we could have huge inequality because individuals vary hugely in their productivity: Some people are just capable of making a contribution hundreds or thousands of times greater than average. This is the view expressed in a widely quoted recent essay by the venture capitalist Paul Graham, and it’s popular in Silicon Valley — that is, among people who are paid hundreds or thousands of times as much as ordinary workers.

Second, we could have huge inequality based largely on luck. In the classic old movie “The Treasure of the Sierra Madre,” an old prospector explains that gold is worth so much — and those who find it become rich — thanks to the labor of all the people who went looking for gold but didn’t find it. Similarly, we might have an economy in which those who hit the jackpot aren’t necessarily any smarter or harder working than those who don’t, but just happen to be in the right place at the right time.

Third, we could have huge inequality based on power: executives at large corporations who get to set their own compensation, financial wheeler-dealers who get rich on inside information or by collecting undeserved fees from naïve investors.

As I said, the real economy contains elements of all three stories. It would be foolish to deny that some people are, in fact, a lot more productive than average. It would be equally foolish, however, to deny that great success in business (or, actually, anything else) has a strong element of luck — not just the luck of being the first to stumble on a highly profitable idea or strategy, but also the luck of being born to the right parents.

And power is surely a big factor, too. Reading someone like Mr. Graham, you might imagine that America’s wealthy are mainly entrepreneurs. In fact, the top 0.1 percent consists mainly of business executives, and while some of these executives may have made their fortunes by being associated with risky start-ups, most probably got where they are by climbing well-established corporate ladders. And the rise in incomes at the top largely reflects the soaring pay of top executives, not the rewards to innovation.