Core inflation is different from headline inflation because the former

Correct — A, (a) ignores articles of volatile nature in the price index. Headline inflation is the rate of change of the whole price index, every group in the basket included. Core inflation is what is left when the groups whose prices swing hardest — food, and fuel and energy — are taken out.

The reason for taking them out is not that they matter less to households. It is that their movements are mostly supply-driven and mostly temporary, and therefore say very little about where inflation is heading. A failed monsoon lifts vegetable prices for a season and a good one drops them back; global crude moves on decisions taken far from the domestic economy; administered prices step up in jumps on the day a rate is revised. A central bank reading such a series month by month would be chasing noise, tightening on a bad tomato crop and easing on a good one, and its instrument works with a lag long enough that the shock would have reversed itself before the policy bit.

Stripping those groups out leaves a measure of the persistent, demand-driven component of inflation — the part that reflects the pressure of aggregate demand on capacity, that shows up in wage settlements and in the prices of services, and that monetary policy can actually influence. Core inflation is therefore used as a gauge of underlying momentum and of second-round effects: if a food-price shock has begun to leak into the prices of everything else, core will rise, and that is the signal that the shock is no longer temporary.

Two qualifications keep the concept honest. First, core is defined by exclusion, so what counts as core depends on what you exclude; in India the working measure is the consumer price index excluding the food and beverages group and the fuel and light group, and it is a derived series rather than an official published target. Second, India's monetary policy framework targets headline consumer price inflation, not core — the Reserve Bank sets policy against the all-items index and reads core alongside it as a diagnostic. Both facts are consistent with option (a), which says only what core does: it leaves the volatile articles out of the reckoning.

Why the others are wrong

• (b)considers articles of volatile nature in the price index — This is the exact reverse of the definition, and it is the option the Commission has printed to catch a candidate reading at speed. Options (a) and (b) are identical except that one says 'ignores' and the other says 'considers', so the entire item comes down to reading a single verb. What option (b) describes is headline inflation, which includes every group in the basket, volatile ones included — so it describes the thing core inflation is being contrasted with, not core inflation itself.
• (c)is not based on commodity price index — Core inflation is computed from the same price index as headline inflation; the only difference is that certain groups are dropped from the basket before the rate of change is taken. It is not an independently constructed measure and it is not built on something other than an index of prices. A candidate can also see that this option, even if true, would not answer the question: the stem asks why core differs from headline, and 'it is not based on a price index at all' would make the two incomparable rather than different by a defined exclusion.
• (d)considers only core items of consumption in the price index — This is the most attractive of the three, because it explains the word 'core' by reading it as 'essential' — the core items of consumption, the things a household cannot do without. That reading is precisely backwards. Food and fuel are the most essential items in any household's budget, and they are exactly the two groups that core inflation leaves out. 'Core' here means the core of the inflation process, the persistent component, not the core of consumption. The measure is defined by what is excluded and why, not by any judgment about which goods matter most to people — which is why core inflation can look comfortable in a month when households are feeling the price rise most sharply.

Headline inflation is the year-on-year change in an all-items price index. Core inflation is the same computation on a restricted basket, from which the components with the highest short-run variance — food, and fuel and energy — have been removed. The purpose is to separate signal from noise. Shocks to food and energy prices are typically supply-side, large, and self-reversing, so a policy authority that reacted to each of them would be adding volatility rather than removing it, especially since monetary policy affects output and prices only with a substantial lag. Core is therefore treated as a measure of underlying or persistent inflation and as an early warning of second-round effects, which is what happens when a relative-price shock in food or fuel begins to raise the prices of unrelated goods and services and to feed into wage expectations. In India the standard construction is the consumer price index excluding the food and beverages group and the fuel and light group; some analysts also strip out petrol and diesel from the miscellaneous group, and there is no single official core series. Since the amendment of the Reserve Bank of India Act, the country runs a flexible inflation targeting framework in which the Central Government, in consultation with the Reserve Bank, notifies an inflation target in terms of the consumer price index once in five years, and a Monetary Policy Committee sets the policy rate to meet it. That target is stated in headline terms, at 4 per cent with a tolerance band of two percentage points on either side — so core informs the judgment without being the thing that is targeted.

Key facts

• Headline inflation is measured on the whole basket of the price index; core inflation excludes the most volatile groups.
• The groups excluded are food and beverages, and fuel and energy — the two whose prices move most on supply shocks.
• The rationale is that food and fuel shocks are largely transitory and supply-driven, while monetary policy acts with a lag.
• Core inflation is read as a measure of persistent, demand-driven inflation and as a signal of second-round effects.
• In India the usual construction is the consumer price index excluding the food and beverages group and the fuel and light group.
• There is no single official core inflation series in India; the measure is derived rather than published as a target.
• India's flexible inflation targeting framework is stated in headline consumer price index terms — 4 per cent, with a tolerance band of two percentage points either side.
• Under the amended Reserve Bank of India Act, the Central Government determines the inflation target in consultation with the Reserve Bank, once in five years, and the Monetary Policy Committee sets the policy rate.
• Food and fuel are the most essential items in a household budget, which is why 'core' must not be read as meaning 'essential'.

Common traps

• Reading 'core' as 'essential' and concluding that core inflation covers necessities; it excludes food and fuel, which are the necessities.
• Missing that options (a) and (b) differ by one verb and marking the first that looks familiar.
• Assuming India targets core inflation; the target is set on the headline consumer price index.
• Treating core inflation as an officially published Indian series with a fixed definition; it is derived, and definitions differ on whether petrol and diesel are also stripped out.
• Concluding that a low core reading means households are not feeling inflation — the two can diverge sharply during a food or fuel shock.

• practice — not a real PYQ

  Core inflation in India is most commonly measured as

  • (a)the Wholesale Price Index excluding manufactured products
  • (b)the Consumer Price Index excluding the food and beverages group and the fuel and light group
  • (c)the change in the GDP deflator
  • (d)the Consumer Price Index for Industrial Workers

  Answer(b) the Consumer Price Index excluding the food and beverages group and the fuel and light group

• practice — not a real PYQ

  Under India's flexible inflation targeting framework, the inflation target is

  • (a)fixed by the Monetary Policy Committee in terms of core inflation
  • (b)determined by the Central Government in consultation with the Reserve Bank, in terms of the Consumer Price Index, once in five years
  • (c)fixed by the Reserve Bank alone in terms of the Wholesale Price Index
  • (d)set annually by Parliament in the Finance Act

  Answer(b) determined by the Central Government in consultation with the Reserve Bank, in terms of the Consumer Price Index, once in five years