Steven Pinker argues that by every possible measure, every type of violence has drastically decreased since ancient and medieval times. A few centuries ago, for example, genocide was a standard practice in all kinds of warfare and was so common that historians did not even bother to mention it. Cannibalism and slavery have been greatly reduced in the last thousand years, and capital punishment is now banned in many countries. According to Pinker, rape, murder, warfare and animal cruelty have all seen drastic declines in the 20th century. Pinker's analyses have also been criticized, concerning the statistical question of how to measure violence and whether it is in fact declining.