Much attention in recent years has understandably focused on the rapid increase in the prison population on both sides of the Atlantic. The fact that the population imprisoned in the United States now exceeds 2 million has been widely referred to, while the prison population in England and Wales increased by 50 per cent between 1993 and 2000. There is also a growing sense among criminologists that the penal system is undergoing a significant transformation. Various explanations have been presented in the past to account for these developments, but few have been found to be convincing (see Matthews, 1999, chapter 6). In the recent period, however, an additional set of explanations have been put forward to explain these changes, and these accounts are gaining considerable ground as plausible explanations.