There are two possible growth areas for prison privatization: expansion within existing markets and entry into completely new ones. Existing markets are found only in developed, westernized, anglophone nations – the USA, the UK and Australia, with New Zealand committed and Canada dipping its toe in the water. The extent of likely expansion in these countries will depend upon a variety of factors which should by now be familiar. Included in these is public and political confidence that private prisons will be effectively accountable. A model for accountability is thus not merely ethically essential in itself but pragmatically important because it will have a bearing upon future growth.