Index numbers

Index numbers measure changes or differences, typically changes over time. For example, changes in average wages over time (the Average Earnings Index (AEI)) and changes in labour costs (the Index of Labour Costs per Hours). An economic index number is an average of the many different changes in price (for example wages) or quantity of the goods and services (for example employees) included in the index. Different methods are used to calculate the average depending on the data and the intended use of the index.