On optimal choices

It's a plus that we're seeing some discussion in Canada as to the optimal income tax rate to maximize revenue. But Paul Krugman goes a step further in pointing out why that revenue-maximizing rate (however calculated) is the optimal rate period:

In the first part of the paper, (Peter Diamond and Emmanuel Saenz) analyze the optimal tax rate on top earners. And they argue that this should be the rate that maximizes the revenue collected from these top earners — full stop. Why? Because if you’re trying to maximize any sort of aggregate welfare measure, it’s clear that a marginal dollar of income makes very little difference to the welfare of the wealthy, as compared with the difference it makes to the welfare of the poor and middle class. So to a first approximation policy should soak the rich for the maximum amount — not out of envy or a desire to punish, but simply to raise as much money as possible for other purposes.
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(T)extbook economics says that in a competitive economy, the contribution any individual (or for that matter any factor of production) makes to the economy at the margin is what that individual earns — period. What a worker contributes to GDP with an additional hour of work is that worker’s hourly wage, whether that hourly wage is $6 or $60,000 an hour. This in turn means that the effect on everyone else’s income if a worker chooses to work one hour less is precisely zero. If a hedge fund manager gets $60,000 an hour, and he works one hour less, he reduces GDP by $60,000 — but he also reduces his pay by $60,000, so the net effect on other peoples’ incomes is zip.

Of course, he doesn’t actually lose all of that $60,000, since he ends up paying less in taxes. So there is a loss of revenue from that withdrawal of effort. But that’s precisely what the Diamond-Saez calculation takes into account, and the reason the optimal top tax rate isn’t 100%.

So, are conservatives comfortable with this analysis? I would guess not, that they have a deep-seated belief that the 1%, by working harder, are doing the 99% a big favor, creating jobs and raising incomes — and that this gain isn’t fully (or even largely) captured by the money they’re paid.

My point, then, is that this claim — and the lionization of high earners as people who make a vast contribution to society — is not, in fact, something that comes out of the free-market economic principles these people claim to believe in. Even if you believe that the top 1% or better yet the top 0.1% are actually earning the money they make, what they contribute is what they get, and they deserve no special solicitude.

[Edit: fixed typo.]