Some of the commenters on Levitt's article claim that Levitt is just kidding when he says Krugman has no sense of humor and hasn't published any academic papers in a long time. Krugman obviously doesn't think he's kidding - and I trust Krugman's instincts more than a bunch of libertarians.
This isn't the first time I've noted that Levitt is a douchebag. Back in December 2008 I asked How big of a douchebag is Steven D. Levitt? for his cold-blooded and tone-deaf comparison of the cost of prostitution services to the cost of rice.
In October of 2009, Amanda Hess of the late great The Sexist asked The Happy Hooker, Or Why Doesn’t Steven Levitt Suck Dick For a Living? for his mind-boggling attitudes about sexuality, women, and the sex trade. The entire column (with Tigerbeatdown's Sady Doyle) is a masterpiece, but this is my favorite part:
AMANDA: yeah. here’s another little pet peeve of mine: pretending that “prostitution” is the same as “sex.” I understand that prostitution is a lot different than it was 100 years ago, and a lot of that has to do with changes in attitudes toward sex. but when these researchers say that prostitutes now see competition from “any woman who is willing to have sex with a man for free,” they’re implying that tons of women are actually performing the work of a prostitute on a daily basis, which is absolutely not the case.
Now the article doesn't come out and say Levitt's a douchebag, but it's clearly implied. One thing we do know - he sure spends alot of time thinking about how to get a good value from prostitutes.
But back to the mighty Krug-man's paper. One of my favorite parts, but you should read the whole thing, it's short:
...the proper modelling of arbitrage in interstellar capital markets where - or when (which comes to the same thing) - simultaneity ceases to have an unambiguous meaning.
These complications make the theory of interstellar trade appear at first quite alien to our usual trade models; presumeably it seems equally human to alien trade theorists..."