The consumer price index measures how prices of things people buy change over time. It looks at food, non-food items, and services to show inflation. This is different from the overall inflation rate, which includes all sectors of the economy. The index is calculated using surveys and price data, and is weighted based on spending habits. The Laspeyres index is often used for this calculation. Individual and aggregate indices help calculate the consumer price index and the general price index for a country.