Or, “Just because you can’t prove that the top marginal tax rate has a large impact on economic growth doesn’t mean that it doesn’t: just have faith!”
As readers will recall, recently a Congressional Research Service report on the impact of top marginal tax rates was “disappeared” after pressure by the Republican leadership was exerted.  The report (mostly a survey of the literature) found no statistically significant impact of top rates on growth. Yet the Republican JEC (to differentiate it from the JEC under Robert Casey)would have us start from the null hypothesis of there being an effect, and only rejecting that (null) hypothesis when sufficient evidence was found against there being an effect.
Now, the JEC-Republicans have produced a report (well, more like a blogpost) that asserts that CRS should’ve studied the effective rate. Indeed, it may very well have been the case that CRS should’ve undertaken that study. After all, I think most of us think the effective rate is important. Oh, they actually did! (Gravelle, Marples, “Tax Rates and Economic Growth,” Report R42111 (December 2011)).
Conclusion: I think the JEC-Republicans should critique the CRS report that addresses the topic the JEC-Republicans argue the CRS should’ve analyzed (and actually did), rather than the CRS report that addresses exactly what it says it address in its title. (After all, I assume that the JEC-Republicans have access to all the CRS reports.)
But I thank the JEC-Republican staff for the best laugh I have had today.
More on the “disappearance” of the CRS report, by Bruce Bartlett.