Wholesale Price Index (WPI) in India: Structure, Weights, Inflation and ISS Exam Questions

The Wholesale Price Index (WPI) is a major Indian price statistic used to track price movements at the wholesale level. For ISS preparation, WPI is important because it tests index-number construction, group weights, inflation calculation and the difference between wholesale and consumer price measurement.

1. What is WPI?

WPI measures the average movement in wholesale prices of a basket of commodities over time. India's current WPI series uses 2011-12=100 as the base year.

2. Major groups and weights

The 2011-12 WPI series has three major groups. Official documentation gives the following weights:

The weights sum to 100. They determine how changes in individual groups contribute to the overall WPI.

3. The WPI formula

At an aggregate level, WPI can be understood as a weighted combination of group indices:

For a numerical question, keep the weights in the same units and ensure that the group weights sum to 100 before interpreting the result.

• Higher-weight groups have a larger effect on the headline index.
• An index of 120 means the level is 20% above the base-period level.
• Inflation is the rate of change in the index, not the index number itself.

4. WPI inflation and provisional data

WPI inflation is commonly expressed as the percentage change in the index over the corresponding period of the previous year. The Office of the Economic Adviser notes that the latest two months in the WPI data series are provisional and may be revised.

5. WPI versus CPI

The most useful comparison is conceptual: CPI represents consumer-facing price movements, while WPI tracks wholesale price movements for its commodity basket. Their weights and coverage differ, so their inflation rates need not be identical in the same month.

6. Common mistakes students make

• Using CPI weights in a WPI calculation.
• Confusing the WPI base 2011-12 with the current CPI base 2024.
• Calling WPI a measure of household retail inflation.
• Forgetting that provisional WPI observations can be revised.

7. Three important questions

Try each one on your own first, then tap the answer.

Key takeaways

• Know the definition, coverage and official source of the indicator before memorising numbers.
• Separate an index level from its percentage growth or inflation rate.
• Read the reference year, population, classification and weights carefully in numerical questions.
• For current-affairs-linked questions, verify the latest official MoSPI or Government of India release before the examination.