The multiplier is set by central government, and is uniform. Power to set the multiplier in Wales has been devolved to the National Assembly for Wales. A special case exists where a defined special authority can set its own multiplier within centrally defined limits. The only currently qualifying authority is the City of London. The multiplier is increased annually, in April. The increase is capped at the same proportion as the increase in the Retail Prices Index for the month of September the preceding year. When re-valuations take place, the multiplier is adjusted so that the overall change across the country is the same as the Retail Prices Index change.