Law of One Price

Law of one price

An economic rule stating that a given security must have the same price no matter how the security is created. If the payoff of a security can be synthetically created by a package of other securities, the implication is that the price of the package and the price of the security whose payoff it replicates must be equal. If it is unequal, an arbitrage opportunity would present itself.

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Absolute Form of Purchasing Power Parity

A theory stating that the same good or service costs the same amount regardless of the currency in which it is measured. For instance, if 1 pound is equivalent to 2 dollars, and a widget costs 1 pound in England, then the absolute form of purchasing power parity would state that the same widget would cost 2 dollars in the United States. This concept is also called the law of one price. In securities, any deviations from the absolute form of purchasing power parity create opportunities for arbitrage (profiting from inefficiencies in prices). See also: Purchasing power parity, Currency pair.