Marginal Benefit
What is Marginal Benefit?
Marginal benefit is the additional satisfaction or utility a consumer enjoys from consuming one more unit of a good or service.
Marginal benefit, also known as marginal utility, tends to decrease as more of a good is consumed. This is the concept of diminishing marginal utility. A consumer will continue purchasing a good as long as the marginal benefit exceeds the marginal cost (price). The optimal consumption level is where MB = MC.
Marginal Benefit: a worked example
A student coming off practice values her first bottle of water at $3.00, the second at $1.80, the third at $0.90 and the fourth at $0.20. Those falling numbers are marginal benefits. The machine charges $1.00 per bottle. She buys the first, since 3.00 is above 1.00, and the second, since 1.80 is above 1.00. The third fails, because 0.90 is below 1.00, so she stops at two bottles. Her total benefit is 3.00 + 1.80 = $4.80 and she paid 2 x 1.00 = $2.00, leaving consumer surplus of 4.80 - 2.00 = $2.80.
The mistake students make with marginal benefit
The error is reading diminishing marginal benefit as a claim that the person is getting less happy overall. Total satisfaction keeps climbing as long as marginal benefit stays positive; it only turns down once an extra unit actively makes things worse, like the bottle of water that leaves you queasy. Diminishing means each new unit adds less than the one before it, not that the running total is falling. The word invites the wrong reading, so check whether the question asks about the extra unit or the total.
Marginal Benefit questions
Is marginal benefit the same thing as price?
Marginal benefit and price are equal only at the last unit a consumer chooses to buy. For every unit before that one, marginal benefit sits above the price paid, and the vertical gap between them is that unit's consumer surplus. This is why a demand curve doubles as a marginal benefit curve: the height of demand at each quantity shows what a buyer would pay for that particular unit, not what she actually hands over.
How do you calculate marginal benefit from total benefit?
Marginal benefit equals the change in total benefit divided by the change in quantity. If total utility rises from 40 utils at 3 units to 46 utils at 4 units, the marginal benefit of the fourth unit is (46 - 40) / (4 - 3) = 6 utils. When a table skips quantities the division matters: going from 3 units to 5 units while total utility rises from 40 to 50 gives (50 - 40) / 2 = 5 utils per unit.
Can marginal benefit be negative?
Marginal benefit turns negative when an extra unit leaves a person worse off, and that is exactly the point where total utility peaks and starts to fall. A sixth slice of pizza that makes you uncomfortable carries negative marginal benefit. No buyer knowingly pays for a unit with negative marginal benefit, which is why the demand curve is drawn over the range where marginal benefit is still positive.
Related terms
Common comparisons
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