Consumer Price Index (CPI) measures the percentage change over time in the cost of purchasing a constant “basket” of goods and services representing the average pattern of purchases made by a particular population group in a specified period of time. The “basket” is of an unchanging or equivalent quality and quantity of goods and services, consisting of items for which there are continually measurable market prices over time. Changes in the costs of items in the “basket” are therefore due only to “pure” price movements, i.e. price movements that are not associated with changes in the quality and/or quantity of the set of consumer goods and services in the “basket”.
The “basket” covers a wide range of goods and services, classified according to the United Nations “Classification of Individual Consumption According to Purpose (COICOP)” in the following thirteen groups: