The relationship between money and prices has historically been associated with the quantity theory of money. There is strong empirical evidence of a direct relationship between the growth of the money supply and long-term price inflation, at least for rapid increases in the amount of money in the economy. For example, a country such as Zimbabwe which saw extremely rapid increases in its money supply also saw extremely rapid increases in prices (hyperinflation). This is one reason for the reliance on monetary policy as a means of controlling inflation.