The Irish have traditionally been involved in the building trade and transport particularly as dockers, following an influx of Irish workers, or navvies, to build the British canal, road and rail networks in the 19th century. This is largely due to the flow of emigrants from Ireland during the Great Famine of 1845–1849. Many Irish servicemen, particularly sailors, settled in Britain: During the 18th and 19th century a third of the Army and Royal Navy were Irish. The Irish still represent a large contingent of foreign volunteers to the British military. Since the 1950s and 1960s in particular, the Irish have become assimilated into the British population. Emigration continued into the next century; over half a million Irish went to Britain in World War II to work in industry and serve in the British armed forces. In the post-war reconstruction era, the numbers of immigrants began to increase, many settling in the larger cities and towns of Britain. According to the 2001 census, around 850,000 people in Britain were born in Ireland.