Which index is used to measure average earnings?

The National Average Earnings Index (NAEI) is specifically designed to measure average earnings across various sectors of the economy. It provides insights into wage trends and earnings shifts, which are crucial for understanding economic conditions and planning for financial security.

In contrast, the Consumer Price Index (CPI) measures inflation by tracking the changes in price levels of a basket of consumer goods and services, serving as an economic indicator but not focusing on earnings directly. The Retail Price Index (RPI) also deals with inflation but includes housing costs, providing a wider perspective on the overall cost of living rather than average earnings. The Producer Price Index (PPI) tracks changes in selling prices received by domestic producers for their output, reflecting price changes at the wholesale level, which again does not pertain to average earnings.

Thus, the NAEI stands out as the relevant index for measuring average earnings, making it the correct choice for this question.