Efficiency Principle

The efficiency principle is an economic tenet that states any action achieves the greatest benefit to society when the marginal benefits from the allocation of resources are equivalent to its marginal social cost.

The efficiency principle lays the theoretical groundwork for cost-benefit analysis, which is how most decisions regarding the allocation of resources are made.

This principle also is at the heart of allocative efficiency, the perfect state where every good or service is produced up to the point where the last unit provides a marginal benefit that is equal to its marginal production cost. At this magical point, which almost never is achieved, there is no deadweight loss, or misused resources.

The efficiency principle leverages many basic tenets underlying economics, including that consumers make decisions and trade-offs at the margin, meaning they carefully weigh the benefits of buying one additional unit of a given item. Moreover, they are rational, meaning consumers will either choose the cheaper product when comparing two of equal benefit, or the one with the most benefits if the items are priced equally.

At the aggregate level, the efficiency principle holds that the the net result of all consumers making rational decisions results in the best possible benefit to society, in dollar terms, with total production at its lowest possible cost. To the contrary, reallocating the goods or producing them inefficiently, where there are too many of one good and not enough of another creates market distortion.

The efficiency principle is central to the study of economics, but there is no practical economic indicator associated with it. There simply are too many assumptions that must be made to determine marginal social costs. There is no government agency that tracks allocative efficiency, and if there was, almost no one would believe the agency’s conclusions.

Let’s say, for example, that a lemonade stand, which sells only lemonade and chocolate-chip cookies, represents the economy. Lemonade costs $1 a glass and cookies are $0.50 each. Given the total underlying supply of lemons, sugar, chocolate chips and labor, the stand can produce a total of 75 cups of lemonade and 50 cookies in a given time frame at a cost of $20. In this scenario, let's also assume market demand is for only 75 cups of lemonade and 50 cookies.

Under the efficiency principle, total output should be $100, or $75 from the lemonade and $25 from the cookie, and profit should be $80, or the $100 in revenue minus costs of $20. If the total output is less than $100, there is deadweight loss somewhere in the economy. Moreover, if the stand produces any other combination of lemonade and cookies, the result will be inefficient. It will not meet total demand at the lowest possible cost, and will not achieve the best-possible $80 benefit.