Computer bugs and Excel mishaps are inevitable because code is written by humans and even brilliant economists aren’t perfect. But careful researchers catch important mistakes; they debug their work until the remaining bugs don’t change the result very much when they are fixed. In both the Piketty and Reinhart and Rogoff cases, it seems the bugs exposed didn’t change their original results. This explains why, while most people assume a bug is a sign of unforgivable sloppiness, economists shrug, point out the results didn’t change much, and think that’s an adequate defense. The economists are right; the existence of a bug isn’t necessarily a big deal.