Since 1950, every constituency has been represented by a single Member of Parliament. There remains a technical distinction between county and borough constituencies; its only effects are on the amount of money candidates are allowed to spend during campaigns and the rank of the local authority co-opted Returning Officer who presides over the count. Geographic boundaries are determined by four permanent and independent Boundary Commissions, one each for England, Wales, Scotland, and Northern Ireland. The commissions conduct general reviews of electoral boundaries once every 8 to 12 years, and interim reviews. In drawing boundaries, they are required to prefer local government boundaries, but may deviate from these to prevent great disparities in electorate; such disparities are given the formal term malapportionment. The proposals of the Boundary Commissions are subject to parliamentary approval, but may not be amended. After their next Periodic Reviews, the Boundary Commissions will be absorbed into the Electoral Commission, which was established in 2000. As of 2019, the UK is divided into 650 constituencies, with 533 in England, 40 in Wales, 59 in Scotland, and 18 in Northern Ireland.