Imperfect information in the context of "Common knowledge (logic)"

Social choice theory is a branch of welfare economics that extends the theory of rational choice to collective decision-making. Social choice studies the behavior of different mathematical procedures (social welfare functions) used to combine individual preferences into a coherent whole. It contrasts with political science in that it is a normative field that studies how a society can make good decisions, whereas political science is a descriptive field that observes how societies actually do make decisions. While social choice began as a branch of economics and decision theory, it has since received substantial contributions from mathematics, philosophy, political science, and game theory.

Real-world examples of social choice rules include constitutions and parliamentary procedures for voting on laws, as well as electoral systems; as such, the field is occasionally called voting theory. It is closely related to mechanism design, which uses game theory to model social choice with imperfect information and self-interested citizens.

Indicative planning is a form of economic planning implemented by a state in an effort to solve the problem of imperfect information in market economies by coordination of private and public investment through forecasts and output targets. The resulting plans aim to supply economically valuable information as a public good that the market by itself cannot disseminate, or where forward markets are nonexistent. However, indicative planning takes only endogenous market uncertainty into account, plans the economy accordingly, and does not look into exogenous uncertainty like technology, foreign trade, etc. Indicative plans serve to complement and enhance the market, as opposed to replace the market mechanism, hence they are adopted in market-based and mixed economies and were most widely practiced in France and Japan before the 1980s. When utilizing indicative planning, the state employs "influence, subsidies, grants, and taxes [to affect the economy], but does not compel". Indicative planning is contrasted with directive or mandatory planning, where a state (or other economic unit) sets quotas and mandatory output requirements. Planning by inducement is often referred to as indicative planning.