The county of Durham has returned 7 MPs to the UK Parliament since 1983. Under the Local Government Act 1972, which came into effect on 1 April 1974, the boundaries of the historic/administrative county were significantly altered with the north-east of the county, comprising more than half the electorate, being transferred to the new metropolitan county of Tyne and Wear. In addition, the borough of Hartlepool was included in the new county of Cleveland. These changes were reflected in the following redistribution of parliamentary seats which did not come into effect until the 1983 general election, resulting in a reduction in the county's representation from 16 to 7 MPs.