Retail Price Index
In the United Kingdom, the Retail Prices Index or Retail Price Index (RPI) is a measure of inflation published monthly by the Office for National Statistics. It measures the change in the cost of a representative sample of retail goods and services.
As the RPI was held not to meet international statistical standards, since 2013 the Office for National Statistics no longer classifies it as a "national statistic", emphasising the Consumer Price Index instead. However, as of 2018 the UK Treasury still uses the RPI measure of inflation for various index-linked tax rises.