Based on population within actual city boundaries the City of Birmingham, the most populous local government district in Europe, is substantially larger than the City of Manchester, which is the fifth largest in the UK (2006 estimates, see List of English districts by population). However, most sources do not use formal city boundaries as the sole criterion for population comparison. The surrounding conurbations and the areas that can be considered informally part of each city are hard to define. However, after the 1974 reorganisation of local government and the creation of metropolitan counties, the City of Birmingham was included with the City of Coventry and five other metropolitan boroughs (one, Wolverhampton gained city status in 2000) in a new West Midlands county. The City of Manchester joined with the neighbouring City of Salford and eight other Metropolitan boroughs within the County of Greater Manchester.