The Economics of Soaking the Rich

What does Alexandria Ocasio-Cortez know about tax policy? A lot.

I have no idea how well Alexandria Ocasio-Cortez will perform as a member of Congress. But her election is already serving a valuable purpose. You see, the mere thought of having a young, articulate, telegenic nonwhite woman serve is driving many on the right mad — and in their madness they’re inadvertently revealing their true selves.

Some of the revelations are cultural: The hysteria over a video of AOC dancing in college says volumes, not about her, but about the hysterics. But in some ways the more important revelations are intellectual: The right’s denunciation of AOC’s “insane” policy ideas serves as a very good reminder of who is actually insane.

The controversy of the moment involves AOC’s advocacy of a tax rate of 70-80 percent on very high incomes, which is obviously crazy, right? I mean, who thinks that makes sense? Only ignorant people like … um, Peter Diamond, Nobel laureate in economics and arguably the world’s leading expert on public finance (although Republicans blocked him from an appointment to the Federal Reserve Board with claims that he was unqualified. Really.) And it’s a policy nobody has every implemented, aside from … the United States, for 35 years after World War II — including the most successful period of economic growth in our history.

.. To be more specific, Diamond, in work with Emmanuel Saez — one of our leading experts on inequality — estimated the optimal top tax rate to be 73 percent. Some put it higher: Christina Romer, top macroeconomist and former head of President Obama’s Council of Economic Advisers, estimates it at more than 80 percent.

Where do these numbers come from? Underlying the Diamond-Saez analysis are two propositions: Diminishing marginal utility and competitive markets.

Diminishing marginal utility is the common-sense notion that an extra dollar is worth a lot less in satisfaction to people with very high incomes than to those with low incomes. Give a family with an annual income of $20,000 an extra $1,000 and it will make a big difference to their lives. Give a guy who makes $1 million an extra thousand and he’ll barely notice it.

What this implies for economic policy is that we shouldn’t care what a policy does to the incomes of the very rich. A policy that makes the rich a bit poorer will affect only a handful of people, and will barely affect their life satisfaction, since they will still be able to buy whatever they want.

So why not tax them at 100 percent? The answer is that this would eliminate any incentive to do whatever it is they do to earn that much money, which would hurt the economy. In other words, tax policy toward the rich should have nothing to do with the interests of the rich, per se, but should only be concerned with how incentive effects change the behavior of the rich, and how this affects the rest of the population.

But here’s where competitive markets come in. In a perfectly competitive economy, with no monopoly power or other distortions — which is the kind of economy conservatives want us to believe we have — everyone gets paid his or her marginal product. That is, if you get paid $1000 an hour, it’s because each extra hour you work adds $1000 worth to the economy’s output.