The most basic "classical" transaction motive can be illustrated with reference to the Quantity Theory of Money. According to the equation of exchange "MV" = "PY", where "M" is the stock of money, "V" is its velocity (how many times a unit of money turns over during a period of time), "P" is the price level and "Y" is real income. Consequently, "PY" is nominal income or in other words the number of transactions carried out in an economy during a period of time. Rearranging the above identity and giving it a behavioral interpretation as a demand for money we have