"The Whole Analysis Sounds Pretty Fishy"

An Economist for Obama says some sources of information should not be trusted:

Tax Foundation is NOT a Credible Source, Economists for Obama: As I explained here, it is a right-wing think tank, part of the billionaire-funded Republican propaganda machine. Here's another post describing some of the misinformation they produce.

Greg Mankiw today links to a brief from the Tax Foundation which tries to claim that tax cuts recover up to 40% of their costs through so-called dynamic effects. Although this is still a long, long way from McCain's deluded claim that tax cuts pay for themselves, it is a much bigger effect than Bush's own Treasury Department estimated (less than 10%). This is an effort to argue that McCain's tax proposal wouldn't create deficits quite as massive as the Tax Policy Center's analysis shows.

Where does the TF figure come from? From yet-to-be-published research, which conveniently makes it impossible to fully critique it. It says it is based on a "large sample of tax returns filed by the same taxpayers between 1998 and 2005 and "examined the change in taxpayers' taxable income as reported on their tax forms and the change in their tax rates, after controlling for a variety of non-tax factors." Immediately, one can see the econometric issues, starting with what is the right lag structure and what is the right set of covariates? The whole analysis sounds pretty fishy. If the data is as juicy as it sounds, why didn't the authors just estimate the direct behavioral effects of the 2001 tax changes, treating them as a natural experiment? The fact that they did not makes me suspect that they massaged the analysis to get the results they wanted. Without seeing the paper, I can only speculate.

My big question is, where on Earth did they get such great data? I have never heard of a publicly available panel data on tax returns, although admittedly, this is not my research area. Will this data be released to other researchers so that they can try to replicate the analysis and examine how fragile the results are? (This has become the research standard for major journals.) I am going to hazard a guess that the researchers will say that the data is confidential, so that we'll just have to trust them. But the Tax Foundation doesn't deserve that kind of trust from anyone, Greg Mankiw included.

Update: The author of the post, in comments:

I want to point out that one of the author's took strong issue with the post in comments on our blog and offered to send me the paper (which I hope to get soon). So I may revise my opinion of the paper and even retract my criticisms after further reflection!

But I stand by the fundamental point that outfits like the Tax Foundation don't get the benefit of the doubt when publicizing results based on unpublished research.