Government's Retail Prices Index (RPI) inflation target of 2.5%. The target changed to 2% in December 2003 when the Consumer Price Index (CPI) replaced the Retail Prices Index as the UK Treasury's inflation index. If inflation overshoots or undershoots the target by more than 1%, the Governor of the Bank of England is required to write a letter to the Chancellor of the Exchequer explaining why, and how he will remedy the situation. The success of inflation targeting in the United Kingdom has been attributed to the Bank's focus on transparency. The Bank of England has been a leader in producing innovative ways of communicating information to the public, especially through its Inflation Report, which have been emulated by many other central banks. Inflation targeting then spread to other advanced economies in the 1990s and began to spread to emerging markets beginning in the 2000s. European Central Bank Although the ECB does not consider itself to be an inflation-targeting central bank, after the inception of the euro in January 1999, the objective of the European Central Bank (ECB) has been to maintain price stability within the Eurozone. The Governing Council of the ECB in October 1998 defined price stability as inflation of under 2%, "a year-on-year increase in the Harmonised Index of Consumer Prices (HICP) for the euro area of below 2%" and added that price stability "was to be maintained over the medium term". The Governing Council confirmed this definition in May 2003 following a thorough evaluation of the ECB's monetary policy strategy. On that occasion, the Governing Council clarified that "in the pursuit of price stability, it aims to maintain inflation rates below, but close to, 2% over the medium term". Since then, the numerical target of 2% has become common for major developed economies, including the United States (since January 2012) and Japan (since January 2013). In 2021, the ECB tweaked its inflation target to a symmetrical 2%. Emerging markets In 2000, Frederic S. Mishkin concluded that "although inflation targeting is not a panacea and may not be appropriate for many emerging market countries, it can be a highly useful monetary policy strategy in a number of them". Armenia The Central Bank of Armenia (CBA) announced in 2006 that it will implement an inflation targeting strategy. The process of full transition to inflation targeting was supposed to end in 2008. Operational, macroeconomic and institutional preconditions for inflation