What does it mean that retail prices were introduced in Britain in 1947?

The Retail Price Index (RPI) is one of the two main measures of consumer inflation produced by the United Kingdom's Office for National Statistics (ONS). It is not considered an official statistic by the U.K., but it is used for certain types of cost escalation. The RPI was introduced in the U.K. in 1947, and it was made official in 1956. Detail:The Retail Price Index (RPI) is an older measurement of inflation that is still published because it is used to calculate cost of living and wage escalation; however, it is not considered an official inflation rate by the government. RPI was first calculated for June 1947, largely replacing the previous Cost of Living Index. It was once the principal official measure of inflation. However, the consumer prices index (CPI) now largely serves that purpose in practice

False but idk if im right