Professor Krugman made my day by confessing to be a Ulysses Grant admirer. Someday we Grantistas should come out of the woodwork and have a convention.

More important, maybe — there was a study released in 2010 about how government debt caused unemployment, as I understand it. This study, called Reinhart/Rogoff after its authors, was seized upon by conservatives to bolster their argument that the “debt crisis” is our primary economic problem, calling for strict austerity. This study has been enormously influential, apparently. Well, turns out the study is bogus. Krugman writes,

According to the review paper, R-R mysteriously excluded data on some high-debt countries with decent growth immediately after World War II, which would have greatly weakened their result; they used an eccentric weighting scheme in which a single year of bad growth in one high-debt country counts as much as multiple years of good growth in another high-debt country; and they dropped a whole bunch of additional data through a simple coding error.

Fix all that, say Herndon et al., and the result apparently melts away.

Further, the response from R and R to the criticism has been really stupid.

There also appear to be issues with bad Excel coding. See, again, Krugman, and also Rortybomb.