(4) There are several ways to measure inflation. On the basis of population coverage,the inflation indices are developed to understand the levels of inflation for certain sets of population such as consumers, producers,retailers, wholesalers etc. Such indices are called Consumer Price Index (CPI),Producer Price Index (PPI),Wholesale Price Index (WPI)etc. On the basis of items,the inflation indices are developed to understand the levels of inflation for certain sets / baskets of items. Since the prices of some items are more volatile than others like food and fuel, it might give conflicting signals to policymakers as the overall inflation could change because of a selected few goods. Hence, separate indices can be developed separating the volatile items from the main index. This gives rise to concepts of Headline inflation and core inflation whereby, the Headline inflation includes al l the items and core inflation usually excludes food and fuel items. There is another variant of core inflation called mean inflation. In this, the components that show the most extreme monthly price changes are excluded.