First raised as a fundamental principle of microeconomics by French economist Leon Walras (1834-1910), demand theory is the analysis of the relationship between the demand for goods or services and prices or incomes.
Demand theory examines purchasing decisions of consumers and the subsequent impact on prices.
The theory was subsequently developed by English economist Alfred Marshall (1842-1924), Italian Vilfredo Pareto (1848-1923), Soviet Eugen Slutsky (1880-1948), American Kenneth Arrow (1921- ) and the French-born Gerard Debreu (1921- ).
L Walras, Elements d'economie politique pure (Lausanne, 1876);
A Marshall, Principles of Economics (London, 1890)