Different concepts of potential GDP

For serious macroeconomists, the magnitude (or existence) of the output gap is a central factor for determining the appropriate policy actions (see for instance Weidner and Williams). In several recent posts, I've discussed the variety of approaches to estimating the output gap [0] [1]. A recent symposium on Projecting Potential Growth published by the Federal Reserve Bank of St. Louis is an excellent resource for anybody who wants to think seriously and carefully about the challenges in estimating this variable. In the lead article entitled "What Do We Know (And Not Know) About Potential Output?", the authors John Fernald and Susanto Basu write:

To keep the discussion manageable, we confine our discussion of potential output to neoclassical growth models with exogenous technical progress in the short and the long run; we also focus exclusively on the United States. We make

The Business Cycle Dating Committee of the National Bureau of Economic Research announced today that the eleventh U.S. postwar recession began in December of 2007.

As has often been the case historically, the announcement itself is a bit anticlimactic, in that pretty much everybody had already reached the same conclusion. I was interested to see that the Business Cycle Dating Committee explained the apparent non-recessionary behavior of real GDP in 2008:Q1-Q2 just as we did last September in terms of the statistical discrepancy between GDP and GDI. From the NBER:

The committee believes that the two most reliable comprehensive estimates of aggregate domestic production are normally the quarterly estimate of real Gross Domestic Product and the quarterly estimate of real Gross Domestic Income, both produced by the Bureau of Economic Analysis. In concept, the two should be the same, because sales of products generate income for