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Allocative efficiency is a type of economic efficiency in which economy/producers produce only those types of goods and services that are more desirable in the society and also in high demand. According to the formula the point of allocative efficiency is a point where marginal benefit is equal to marginal cost (MB=MC). At this point the social surplus is maximized with no deadweight loss, or the value society puts on that level of output produced minus the value of resources used to achieve that level, yet can be applied to other things such as level of pollution. Free markets under perfect competition generally are allocatively efficient, yet are not for the cases of monopoly, monopsony, externalities, and public goods which construe market failure, or price controls which construe government failure in addition to taxation. Allocative efficiency is the main tool of welfare analysis to measure the impact of markets and public policy upon society and subgroups being made better or worse off.
Although there are different standards of evaluation for the concept of allocative efficiency, the basic principle asserts that in any economic system, choices in resource allocation produce both "winners" and "losers" relative to the choice being evaluated. The principles of rational choice, individual maximization, utilitarianism and market theory further suppose that the outcomes for winners and losers can be identified, compared and measured.
Under these basic premises, the goal of maximizing allocative efficiency can be defined according to some neutral principle where some allocations are objectively better than others. For example, an economist might say that a change in policy increases allocative efficiency as long as those who benefit from the change (winners) gain more than the losers lose.
It is possible to have Pareto efficiency without allocative efficiency. By shifting resources in the economy, a gain in benefit to one individual could be greater than the loss in benefit to another individual (see Kaldor-Hicks efficiency). Therefore, before such a shift, the market is not allocatively efficient, but might be Pareto efficient.
When a market fails to allocate resources efficiently, there is said to be market failure. Market failure may occur because of imperfect knowledge, differentiated goods, concentrated market power (e.g., monopoly or oligopoly), or externalities.
See also 
- Pareto efficiency
- Production-possibility frontier
- Productive efficiency
- Financial market efficiency