THEORY OF CONSUMER BEHAVIOUR

Utility simply means the satisfaction you get from consuming something. Total utility is the complete satisfaction from consuming all units of a good—like the total happiness from eating five plates of jollof rice. Average utility divides this total satisfaction by the number of units consumed, so you'd divide your total happiness by five plates to get satisfaction per plate.

Marginal utility is the extra satisfaction from consuming one additional unit. Imagine you're very hungry; that first plate of jollof rice gives massive satisfaction. The second plate still feels great, but slightly less exciting. By the fifth plate, you're quite full, so marginal utility drops significantly. This declining marginal utility explains why prices must fall to encourage buying more units.

To calculate: if eating three plates gives 60 units of satisfaction, average utility is 60÷3=20 units per plate. If the fourth plate adds only 10 more units, that's your marginal utility for that plate.

When you buy things, you get satisfaction from them—that's utility. As you consume more of something, say Indomie noodles, your total satisfaction keeps growing. But notice something interesting: the first plate brings massive satisfaction when you're hungry, but by the fifth plate, you're barely enjoying it. That's diminishing marginal utility—the extra satisfaction from each additional unit decreases.

Think about it this way: if you have ₦5,000 to spend on food, you'll buy items that give you the most satisfaction per naira spent. Your first purchase solves your biggest need. Later purchases satisfy smaller wants. This is why smart consumers don't spend all money on one item.

Understanding this helps explain why you stop buying something even when money remains—the satisfaction per naira keeps falling until it's no longer worth it.

When you buy things, you get satisfaction called utility. Total utility is the complete satisfaction you get from consuming all units of a good—like the total joy from eating five balls of rice. Average utility divides this total satisfaction by the number of items consumed. Marginal utility is the extra satisfaction from consuming one more unit. For example, your first plate of jollof rice brings high satisfaction, but the fifth plate brings less joy because you're getting full.

Consumer equilibrium occurs when you spend your money in a way that maximizes your total satisfaction. This happens when the marginal utility per naira spent is equal across all goods you buy. If you're buying both bread and butter, you've reached equilibrium when the last naira spent on bread gives the same satisfaction as the last naira spent on butter.

A consumer reaches equilibrium when they get maximum satisfaction from their money. This happens when the ratio of marginal utility to price is equal for all goods bought. Simply put, the last naira spent on each item gives the same happiness.

Imagine Chioma at a market buying rice and beans. She's in equilibrium when buying one more kilogram of rice gives her the same satisfaction per naira as buying one more kilogram of beans. If rice becomes cheaper, she'll buy more rice because each naira now buys more satisfaction from rice than beans. This is the substitution effect—she switches to the cheaper good.

When price drops, Chioma also feels richer with the same money, so she buys more of everything. This is the income effect. Together, these effects explain why demand increases when price falls.

When you're at Shoprite deciding what to buy with your pocket money, you're naturally aiming for consumer equilibrium. This is the point where you get maximum satisfaction from your money by comparing what each extra naira spent gives you. Marginal utility, which is the satisfaction from buying one more item, directly determines your demand for that product.

Think about buying meat pie at the canteen. Your first pie gives tremendous satisfaction, but the fifth pie gives you almost nothing—you're already full. When marginal utility drops, you demand less. If the price falls, you buy more because that last pie becomes worth it again. This relationship explains why demand curves slope downward: as prices drop, the marginal utility of spending that money justifies buying additional units.