municipal jails. In countries with a federal system of government, such as Brazil, Germany and India, prisons are administered not by the national government but by individual states. The vast majority of prisoners worldwide are adult males. Of these, a minority have committed very serious crimes; it is the responsibility of prison systems to protect the public from such convicts at all costs. Other prisoners are career criminals who regularly commit burglaries and thefts, and who accept that from time to time they will be caught, convicted, and sentenced to a period of imprisonment. Also common among prisoners are people on the margins of society who commit minor offences; they may be drug addicts or alcoholics, they may be mentally disordered, or they may feel that they have lost their place in society through unemployment or homelessness (see alienation). Most prison systems have different sorts of prisons to contain these different groups. For the most serious criminals, there are high-security prisons, where the movement of every prisoner is closely supervised so that they have little chance of escaping. For the majority there are medium-security prisons, where prisoners are expected to work, attend educational programs, or participate in other activities that prepare them for release. Finally, there are prisons that have a very low level of security for those who present no threat to public safety. ]