DEFINITION of 'Purchasing Power Parity-PPP'. An economic theory that estimates the amount of adjustment needed on the exchange rate between countries in order for the exchange to be equivalent to each currency's purchasing power.
Thomas Edison's most famous invention, the lightbulb, paved the way for modern life.
Thomas Edison & The History of Electricity. 1876 was also the year that Thomas Alva Edison opened a laboratory in Menlo Park, New Jersey, where he could explore the possibilities of the dynamo and other electrical devices that he had seen in the Exposition.