Paul Krugman is a liar
"John Lott first attracted notoriety with a pro-gun-ownership study nobody else could duplicate; his original data, he said, was destroyed by a hard disk crash."
1) There is a whole list of studies have duplicated my research on gun control (see here for a slightly out of date list). I even had a letter in Krugman's own New York Times in January pointing this fact out (available here). If Krugman has evidence that these papers that I cite do not duplicate my work, he should provide his evidence.
2) The original data that was used in my regressions was replaced after a hard disk crash and given out to well over a couple hundred academics. David Mustard and I had given out this data to some critics before the crash (Dan Black, Dan Nagin, and Jens Ludwig), but they would not give us back a copy of the data so David and I spent months putting the data back together again. But we did put it back together and we did lend out that data to others, as demonstrated by the papers that have been published by those using the data.
Other unrelated thoughts about Krugman.
Daniel Okrent, New York Times Ombudsman, wrote: "Op-Ed columnist Paul Krugman has the disturbing habit of shaping, slicing and selectively citing numbers in a fashion that pleases his acolytes but leaves him open to substantive assaults."
Paul Krugman Is a Liar: Does the New York Times Care?
Paul Krugman: Idiot or Morally Bankrupt Liar?
Krugman’s Forgotten History
Neil Cavuto Smacks Around Paul Krugman While Calling Him a Liar
How did Paul Krugman get it so Wrong? by John H. Cochrane
"Krugman’s the liar," Donald Luskin NRO
Paul Krugman is a Dangerous Liar
Big Lies and Little Ones, Paul Krugman's only example turns out to have been fraudulent.
Krugman’s a Liar, by Jonathan Adler
George Will Smacks Down Paul Krugman With Simple Reaganomics
Paul Krugman: An Ignoble Liar
UPDATE: For more on Krugman citing Media Matters' claim see this discussion here.