The House of Commons is one of the oldest Parliaments in Europe, and also the most conservative in many ways. This conservatism shows in the electoral system as well, which is based on a rather simple principle: each community elects one representative to serve as its Member of Parliament (MP) until the next general election. Historically, there was a distinction between towns and counties, but nowadays both urban and rural areas are uniformly divided into constituencies.112 The size of these constituencies can be very different: in a densely populated city like London, there are several constituencies consisting only of a few streets, while in sparsely populated rural areas in Scotland, one single constituency may cover an enormous area. To ensure fair representation, the boundaries of the constituencies are reviewed roughly every ten years. Currently there are 650 seats in the Commons, one MP representing about 60,000 to 90,000 voters. The franchise (right to vote) was gradually extended to more and more adult men during the 19th century by several Reform Acts, but all adult men and women received it only in 1918, which greatly helped the Labour Party to become a major party afterwards. Women could not vote until 1918, and their minimum age limit was higher until 1928. In 1970 the minimum voting age for both genders was reduced from 21 to 18. Nowadays, only children, convicted criminals, and the mentally ill are excluded from voting, as well as peers who have the right to sit in the House of Lords. An interesting aspect of the British election rules is that besides British subjects, all citizens of Commonwealth countries or the Irish Republic resident in the UK may also vote at the general elections.