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Social choice theory
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<p>Social choice theory is a branch of <a href="/facts/Welfare_economics/27rrn9UJ">welfare economics</a> that extends the <a href="/facts/Decision_theory/TbXcQX0v">theory of rational choice</a> to collective decision-making. Social choice studies the behavior of different mathematical procedures (<a href="/facts/Social_welfare_function/m5f7lA1t">social welfare functions</a>) used to combine individual preferences into a coherent whole. It contrasts with <a href="/facts/Political_science/Gqy5EoRX">political science</a> in that it is a <a href="/facts/Normative_economics/3mo8HD4c">normative</a> field that studies how a society can make good decisions, whereas political science is a <a href="/facts/Positive_economics/lDGMfowN">descriptive</a> 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 <a href="/facts/Mathematics/pxTouaz4">mathematics</a>, <a href="/facts/Philosophy/zAH5PVD6">philosophy</a>, <a href="/facts/Political_science/Gqy5EoRX">political science</a>, and <a href="/facts/Game_theory/zkEIj1ya">game theory</a>. </p><p>Real-world examples of social choice rules include <a href="/facts/Constitution/GppU7erf">constitutions</a> and <a href="/facts/Parliamentary_procedure/GvMMDIkt">parliamentary procedures</a> for voting on laws, as well as <a href="/facts/Electoral_system/e6zvx3Bo">electoral systems</a>; as such, the field is occasionally called voting theory. It is closely related to <a href="/facts/Mechanism_design/l3Uj6wfe">mechanism design</a>, which uses <a href="/facts/Game_theory/zkEIj1ya">game theory</a> to model social choice with <a href="/facts/Imperfect_information/bouFdU4l">imperfect information</a> and <a href="/facts/Homo_economicus/wsY8sa8D">self-interested</a> citizens. </p><p>Social choice differs from <a href="/facts/Decision_theory/TbXcQX0v">decision theory</a> in that the latter is concerned with how <i>individuals</i>, rather than <i>societies</i>, can make rational decisions. </p>