Krugman’s Weak Defense of High Marginal Tax Rates

Alexandria Ocasio-Cortez recently proposed a 70% marginal tax rate on top income earners. Given that this policy almost doubles the current marginal tax rate, many view the plan as a bit too much. Don’t worry though, because Paul Krugman is here to assure you that actually AOC’s proposal is just espousing standard economics. In fact, “there isn’t any body of serious work supporting G.O.P. tax ideas, because the evidence is overwhelmingly against those ideas.”

I don’t think Krugman is right about that, but before getting to him I should concede a couple points. First, I really don’t think the tax plan AOC is proposing would destroy the economy. Her 70% rate would only kick in at $10 million per year. That hits almost nobody. It’s also a marginal rate not an average rate so it doesn’t mean that rich people are giving 70% of their total income to the government, only income above $10 million. Most rich people aren’t making the majority of their money through wages anyway so the effects of this plan probably aren’t huge either way (note that also means it won’t raise very much revenue).

Krugman, however, is making a much stronger claim. He’s not only arguing that more progressive taxes are better, but that there isn’t any support for the idea that low taxes can be good. Here’s an excerpt from a 2009 JEP article summarizing key findings from the optimal taxation literature:

1) Optimal marginal tax rate schedules depend on the distribution of ability; 2) The optimal marginal tax schedule could decline at high incomes; 3) A flat tax, with a universal lump-sum transfer, could be close to optimal; 4) The optimal extent of redistribution rises with wage inequality; 5) Taxes should depend on personal characteristics as well as income; 6) Only final goods ought to be taxed, and typically they ought to be taxed uniformly; 7) Capital income ought to be untaxed, at least in expectation; and 8) In stochastic dynamic economies, optimal tax policy requires increased sophistication. For each lesson, we discuss its theoretical underpinnings and the extent to which it is consistent with actual tax policy.

Mankiw et al, 2009

Funny enough, 2, 3, 6, and 7 sound strikingly like those GOP tax ideas that Krugman says are entirely unsupported by the economic literature. So maybe he just meant the evidence he already agrees with. Of course, Krugman has his own evidence, which argues that the optimal top marginal tax rate for the US economy is 73%. I admit I haven’t read the paper he references. I’m sure they offer a better justification for that rate than Krugman. His would fail my Econ 1 class. Quoting the relevant section:

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.


In that case, however, why do we care how hard the rich work? If a rich man works an extra hour, adding $1000 to the economy, but gets paid $1000 for his efforts, the combined income of everyone else doesn’t change, does it? Ah, but it does — because he pays taxes on that extra $1000. So the social benefit from getting high-income individuals to work a bit harder is the tax revenue generated by that extra effort — and conversely the cost of their working less is the reduction in the taxes they pay.


Or to put it a bit more succinctly, when taxing the rich, all we should care about is how much revenue we raise. The optimal tax rate on people with very high incomes is the rate that raises the maximum possible revenue.

To summarize what Krugman is saying here: If we ignore the welfare of the rich themselves, we only care about how much they work to the extent that they pay taxes. In other words, if taxes were 0, there is no difference between rich people working 0 hours or a million. The welfare for the rest of us is unchanged.

To anybody but an economist this is obviously ridiculous. Does Krugman really think that if Bill Gates had never worked a day in his life we wouldn’t miss Microsoft or any of the products that it produced? We’d only lose out on the taxes he paid? I don’t think so.

So what’s wrong with Krugman’s analysis? Isn’t it true that all workers in a competitive market get paid their marginal product? And if that’s the case then doesn’t losing their efforts just mean that we only lose what we were paying them anyway? Not exactly. His logic is correct for an infinitesimal (virtually 0) drop in labor, but not for a large change. If rich people are actually doing valuable work and that stops because they are discouraged by taxes, the output of everybody else will fall. If Bill Gates works 1 second less, it’s true that that won’t impact anybody else’s welfare. If Bill Gates never invented Microsoft at all (because he thought the gains were too low to take the risk), hundreds of thousands of people would need to find other (less productive) work. The welfare benefits of Gates’s creations are far far above any compensation he has ever received.

Krugman also ignores the costs on the consumer side from reduced labor. Even if a worker gets paid their marginal product in nominal dollar terms, the output they produce is more valuable to the person who buys it than it is to the person who created it (otherwise the trade wouldn’t have occurred). If taxes reduce the amount people want to work and create new products, this consumer surplus is lost.

This isn’t the first time Krugman has tried to argue that when workers are paid their marginal product then their work has no value to the rest of society because they take everything they put in. Bob Murphy offers an excellent rebuttal in this post. John Cochrane also has a great recent post on the tax issue. His evaluation of Krugman’s argument:

Krugman gets the benefit of labor to society wrong in an astonishing econ 1 way

If you are paid your marginal product, as you are in a competitive market, then you are paid how much revenue your efforts add to your employer’s bottom line. But society benefits by the consumer surplus, the area under the demand curve, and loses that consumer surplus when taxes put a wedge between your effort and your wage. When Steve Jobs worked hard and sold us all Iphones, he made a ton of money, and apple made a huge profit. But we all benefitted by far more than we paid Apple for the phones.

No, the world is not a static, zero-sum game.

Tax policy is hard. I don’t know what the optimal tax rate should be. It could very well be higher than what we have now. But to say that it’s settled economics is misleading if not an outright lie.

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