New Delhi, May 19 (PTI) India's inflation debate appears to be entering a complicated phase. On the surface, retail inflation appears under control, giving consumers and policymakers some relief. But beneath that, wholesale prices rose sharply in April, even before petrol and diesel prices were increased.

The Rs 4 per litre increase in fuel prices in two installments is likely to have an impact on retail inflation that could soon spill over into household budgets. According to various estimates the impact could be around 20 basispoints (bps).

WHAT ARE CPI- AND WPI-BASED INFLATION? ------------------------------------------------- Consumer Price Index (CPI): CPI measures the change in prices paid by consumers for everyday goods and services such as food, housing, transport, healthcare, and education. It is the Reserve Bank of India's (RBI's) primary inflation gauge for monetary policy. Simply put, CPI reflects the inflation ordinary households feel.

Wholesale Price Index (WPI): WPI tracks price movements at the wholesale or producer level before goods reach consumers. It captures changes in prices of fuel, raw materials, metals, chemicals and manufactured products. WPI is often seen as an early warning signal because rising producer costs eventually get passed on to consumers.

APRIL INFLATION NUMBERS? ------------------------------- India's retail inflation, measured by CPI, rose modestly to 3.48 per cent in April 2026 from 3.40 per cent in March, remaining below the RBI's medium-term target of 4 per cent. Food inflation edged up to 4.2 per cent, while core inflation remained relatively stable. Wholesale inflation, however, painted a dramatically different picture.

WPI inflation surged to 8.3 per cent in April -- a 42-month high -- from 3.88 per cent in March, driven largely by soaring fuel and energy prices following the Middle East conflict and disruptions to crude oil supplies. The biggest jump came from the fuel and power category, where inflation shot up to 24.71 per cent from just 1.05 per cent a month earlier. Crude petroleum inflation climbed more than 88 per cent.

FUEL WEIGHT IN WPI, CPI? ----------------------------- Petrol and diesel do not have a standalone category in the CPI basket, but are captured under the broader 'transport and communication' component and 'fuel and power' category. Petrol and diesel carry relatively smaller but still significant weights through transport-related items, and economists say fuel price hikes have a wider indirect impact because they raise freight, logistics and input costs across sectors.

Fuel has a much bigger role in the WPI. Fuel and power category weight is around 13.15 per cent in WPI.

Even though petrol's direct CPI weight is low, fuel prices have a powerful second-round effect across the economy. Higher fuel prices increase transport costs, freight rates, food distribution expenses, farm input costs, manufacturing costs, airline and logistics expenses.

Diesel is especially important because it is India's most-used fuel (around 40 per cent). It powers trucks, buses, agricultural pumps, generators, industrial transport networks. That means a sustained fuel price rise eventually pushes up prices of vegetables, milk, packaged goods, cement, steel, and services.

WHY IS THERE A SHARP DIVERGENCE BETWEEN WPI AND CPI INFLATION? --------------------------------------------------------------------------------- WPI inflation is more sensitive to global commodity price movements and fuel and power basket carry a much higher weight in the WPI. Oil price shock amid the West Asia war has spiked April WPI inflation. In contrast, CPI measures retail prices. It gives a much larger weight to food and services (housing, healthcare, education and transport), while fuel, gas and electricity have a relatively smaller share. Moreover, higher wholesale costs often take time to fully pass through to retail consumers, resulting in a temporary divergence between WPI and CPI inflation.

WHAT IS THE EXPECTATION OF FUTURE INFLATION TRAJECTORY? ------------------------------------------------------------------------ Economists expect wholelsale inflation to remain high in the near term and touch 9 per cent in May as the West Asia crisis continues to keep global crude and commodity prices elevated. The high global prices would gradually feed into domestic fuel, manufacturing and transport costs.

Retail inflation is expected to edge higher in May as costlier fuel, food, transportation, and manufactured goods begin feeding into retail prices. Petrol and diesel prices were raised by Rs 3/litre -- the first time in four years -- adding to inflationary pressures.

Economists said the full impact of the fuel price hike, along with the recent increase in milk prices, is likely to be fully reflected in June CPI inflation data, which will be released in mid-July.

The inflation outlook will also depend on monsoon and the El Nino impact. Any weather-related disruption may further increase pressure on food prices, which have a high weight in the CPI basket.

WHAT WOULD BE THE INTEREST RATE TRAJECTORY GOING FORWARD? ----------------------------------------------------------------------------- Economists expect the RBI to maintain a cautious pause on interest rates in the near term as it assesses the impact of rising crude oil prices and the pass through of wholesale prices into retail prices.

The RBI is expected to keep repo rate on hold at 5.25 per cent for now. The central bank would largely watch out three factors -- the trajectory of global crude oil prices, the monsoon's impact on food inflation, and the impact of fuel price rise and the extent to which wholesale inflation passes through to retail inflation.

In the near term, the RBI is expected to focus on currency stability and inflation control, especially as the rupee remains under pressure. PTI JD ANZ the monsoon and the impact of El Niño TRB