Inflation is the pace at which prices rise over time, the same basket of goods costing more this year than last. India tracks it with two main gauges: the Consumer Price Index (CPI) for the prices you pay in shops, and the Wholesale Price Index (WPI) for prices at the wholesale, business-to-business level.
What do CPI and WPI actually measure?
Kavita's monthly grocery bill was ₹4,000 last year. This year the same items cost ₹4,240. Nothing in her trolley changed. Money simply buys less. That 6% rise, averaged across food, fuel, rent, clothing and more for households across the country, is roughly what CPI captures. It is published every month by the government's statistics office.
WPI measures the same disease at an earlier stage: the prices producers and wholesalers charge each other for commodities, fuel and manufactured goods, before retail margins are added. It is also published monthly.
| Gauge | Whose prices? | Why markets watch it |
|---|---|---|
| CPI | Retail. What households pay | The RBI's inflation target is framed around it |
| WPI | Wholesale. What businesses pay | Early warning on input costs and company margins |
How does an inflation number end up moving stock prices?
The chain runs through the central bank. The Reserve Bank of India (RBI) is legally tasked with keeping CPI inflation inside a target range. When CPI runs hot, the RBI often responds by raising the repo rate, making borrowing costlier to cool demand. Costlier borrowing squeezes company profits and household spending, and markets often react to that prospect the moment the CPI print is released, well before any rate decision.
So a single monthly data release can move indices: a hotter-than-expected CPI number often makes markets nervous about rate hikes, while a cooler number often brings relief. As always, the reaction depends on what was already expected, not on the number in isolation.
Who feels inflation first?
Inflation does not hit every business equally, which is why some sectors often react more to CPI and WPI data:
- FMCG makers (soaps, packaged foods) buy commodity inputs whose prices WPI tracks. When input costs rise faster than they can raise shelf prices, profit margins get squeezed.
- Autos and other big-ticket sellers feel it through the customer: when Kavita's grocery bill and EMIs both swell, a new car is the easiest purchase to postpone.
- Lenders sit on the other side, the RBI's response to inflation resets the rates at which they borrow and lend.
This is also why inflation shapes the tug-of-war between cyclical and defensive stocks: demand-driven businesses tend to feel high inflation sooner than sellers of everyday essentials.
A little inflation, for the record, is normal. Economies are generally run to have modest, steady inflation rather than none. Markets worry when it is too high, accelerating, or stubbornly above target.
Things to keep in mind
- CPI is the number that matters most for RBI policy; WPI is an early read on business costs. The two can diverge for months at a time.
- Markets often react to the gap between the released number and expectations. A "high" print that was fully anticipated may cause no move at all.
- Inflation quietly erodes the real value of idle cash and fixed returns, which is a big reason people invest at all.
- One month's data is noise; trends over several months are what policy and markets ultimately follow.
Read next
What is the repo rate, and why do markets react to RBI policy? — How the central bank answers inflation, and why markets hang on it.