Efficiency Principle

What Does Efficiency Principle Mean?
An economic theory that states that the greatest benefit to society of any action is achieved when the marginal benefits from the allocation of resources are equivalent to the marginal social costs of the allocation.

Investopedia explains Efficiency Principle
The efficiency principle lays the theoretical groundwork for cost-benefit analysis, which is how most critical business decisions regarding the allocation of resources are made. On its own, however, there are simply too many assumptions that must be made to determine "marginal social costs", which makes the usefulness of the efficiency principle questionable in practical terms.