Welfare economics
The concept of welfare is concerned with the well-being of the individual, and the subject matter of welfare economics is the influence of collective decisions upon the welfare of groups of individuals. The theorems of welfare economics constitute the rationale for the criteria of economic efficiency, the theoretical benefits of market competition, and the practice of cost-benefit analysis.
Definition
The definition of the welfare of an individual is the same as the definition of utility that is presented in the article on that subject, but the problem of defining collective or "social" welfare is greatly complicated by the logical impossibility, noted in that article, of making inter-personal comparisons of utility. The nature of that problem is discussed on the tutorials subpage, where it is noted that no completely satisfactory theoretical solution is available. Applied welfare economics consequently provides only partial ad-hoc solutions, qualified by the need to embody value judgments without totally abandoning the presumption that every individual is the sole judge of his own welfare. In many cases, however, the judgements required are so widely accepted as to present no practical difficulty. There is general acceptance, for example, that gains in individual welfare arising from psychotic satisfactions are not admissible components of social welfare.
Fundamental theorems of welfare economics
In a market mechanism with flexible prices, individuals will continue to trade with each other until they reach an optimal outcome. The market provides a mechanism for individuals to communicate their preferences through prices so that each individual will be able to an optimal bundle of consumption given a particular budget constraint.
First theorem of Welfare Economics
In a market with many traders where prices are flexible, any equilibrium will be pareto-optimal.
Second theorem of Welfare Economics
Every outcome that is pareto-optimal can be realized in a market with many traders and flexible prices provided an appropriate initial distribution of endowments.