The announcement of a numerical definition has been devised to enhance clarity, anchor expectations and offer a yardstick against which the ECB can be held accountable. The Governing Council defined price stability as "a year-on-year increase in the Harmonised Index of Consumer Prices for the euro area of below 2%".
The upper bound of 2% is in line with the practice of participating national central banks before the start of Stage Three of Economic and Monetary Union (EMU). It enables the existence of a possible positive measurement bias in the HICP to be taken into account and creates a "safety margin" which helps ensure that negative rates of "true" inflation are avoided.