The wholesale price index (WPI) measures the average monthly price changes of goods sold in bulk between traders. It tracks price changes before the retail level and is used by the Reserve Bank of India and the government to monitor inflation trends and form monetary policies. The WPI is calculated using a fixed base year and Laspeyre's formula, which weights commodity prices by their importance. While it provides timely inflation data, the WPI only covers goods prices and may not accurately reflect consumer prices.