There isn't really a strong theoretical reason. A few I've seen: (1) it seems to be difficult for central banks to implement negative nominal interest rates (

There isn't really a strong theoretical reason. A few I've seen: (1) it seems to be difficult for central banks to implement negative nominal interest rates (cash can go under the matrress), and so a positive inflation target will allow a government a bit more scope to cut interest rates during a recession without running into a 'zero lower bound'. (2) 0% nominal pay rises seem to be a focal point in wage negotiations, and so positive inflation will allow nominal wages to fall in a recession. There are other arguments I have seem, but all seem quite weak. I don't think there is some definitive justification for 2% vs 5% vs. 0% that can be derived from first principals. Milton Friedman actually pointed out some theoretical benefits of negative inflation [1]. https://en.wikipedia.org/wiki/Friedman_rule https://en.wikipedia.org/wiki/Friedman_rule