Notice the pattern.

Step 1: Economics textbooks offer a clever-and-appealing policy proposal: Let’s tax carbon emissions to curtail the serious negative externalities of fossil fuels. It’s cheap, it’s effective, it provides great static and dynamic incentives. Public choice problems? Don’t listen to those naysayers.

Step 2: Argh, Pigovian taxes are going nowhere.

Step 3: Let’s have a trendy-but-awful populist infrastructure program to get the masses on board.

So what? For starters, any smart activist who reaches Step 3 tacitly concedes that public choice problems are dire. You offer the public a clever-and-appealing remedy for a serious social ill, and democracy yawns. To get action, you have to forget about cost or cost-effectiveness – and just try to drug the public with demagoguery.

Note: I’m not attacking Krugman for having little faith in democracy. His underlying lack of faith in democracy is fully justified. I only wish that Krugman would loudly embrace the public choice framework that intellectually justifies his lack of faith. (Or better yet, Krugman could loudly embraced my psychologically-enriched public choice expansion pack).

Once you pay proper respect to public choice theory, however, you cannot simply continue on your merry way. You have to ponder its central normative lesson: Don’t advocate government action merely because a clever-and-appealing policy proposal passes a cost-benefit test. Instead, look at the trendy-but-awful policies that will actually be adopted – and see if they pass a cost-benefit test. If they don’t, you should advocate laissez-faire despite all those shiny ideas in the textbook.

Krugman could naturally reply, “I’ve done the math. Global warming is so terrible that trendy-but-awful policies are our least-bad bet.” To the best of my knowledge, though, this contradicts mainstream estimates of the costs of warming. That aside, why back a Green New Deal instead of deregulation of nuclear power or geoengineering? If recalcitrant public opinion thwarts your clever-and-appealing remedy, maybe you started out on the wrong path in the first place.

Unfair? Well, this is hardly the first time that Krugman has rationalized destructive populism when he really should have reconsidered. Krugman knows that immigration is the world’s fastest way to escape absolute poverty. He knows that standard complaints about immigration are, at best, exaggerated. But he’s still an immigration skeptic, because:

The New Deal made America a vastly better place, yet it probably wouldn’t have been possible without the immigration restrictions that went into effect after World War I. For one thing, absent those restrictions, there would have been many claims, justified or not, about people flocking to America to take advantage of welfare programs.

Notice the pattern.

Step 1: You start with the textbook case for a welfare state to alleviate domestic poverty. Public choice problems? Bah.

Step 2: Next, you decide that you can’t get that welfare state without horrible collateral damage.

Step 3: So you casually embrace the status quo, without seriously engaging obvious questions, like: “Given political constraints, perhaps its actually better not to have the New Deal?” or even “How close can we get to the New Deal without limiting immigration?”