Claim: United Kingdom has the ninth-largest economy by economic theory that states that the exchange rate between two currencies equal the ratio of the currencies' respective purchasing power called purchasing power parity.
Evidence: The United Kingdom is a developed country and has the world 's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity.
Purchasing power parity -LRB- PPP -RRB- is an economic theory that states that the exchange rate between two currencies equal the ratio of the currencies ' respective purchasing power.