Income Effect

The core idea

When the price of something falls, your money goes further even if your salary hasn't moved. That gain in real purchasing power is the income effect: it changes consumption simply because you are effectively richer (or poorer) after the price change. If petrol gets cheaper, the household budget loosens, and families may spend the freed-up rupees on more fuel, more outings, or something else entirely.

Economists split any price change into two parts, the substitution effect (switching toward relatively cheaper goods) and the income effect (the change driven by altered real income). Together they explain the full demand response.

Normal versus inferior goods

The direction of the income effect depends on the type of good. For a normal good, a rise in real income raises demand, so the income effect reinforces the substitution effect and demand clearly rises when price falls.

For an inferior good, demand falls as real income rises, so the income effect works against the substitution effect. Think of a household that leans on a cheap staple when money is tight: when prices drop and the budget eases, it may buy a little less of the basic staple and more vegetables, pulses or meat.

The Giffen extreme

In rare cases the income effect on a strongly inferior good is so powerful that it overwhelms the substitution effect entirely, producing a Giffen good whose demand actually rises when its price rises. The classic illustration is a poor household that spends most of its budget on one staple grain; a price increase makes them poorer overall, forcing them to cut costlier foods and buy even more of the cheap staple.

For everyday Indian life, the income effect helps explain why fuel, food-price and tax changes ripple far beyond the item whose price actually moved.