(3) income of an economy grows on account of an initial investment Explanation: In economics, a multiplier is a factor of proportionality that measures how much an endogenous variable changes in response to a change in some exogenous variable. For example, suppose a one-unit change in some variable x causes another variable y to change by M units. Then the multiplier is M. In monetary macroeconomics and banking, the money multiplier measures how much the money supply increases in response to a change in the monetary base. The multiplier may vary across countries, and will also vary depending on what measures of money are considered. For example, consider M2 as a measure of the U.S. money supply, and MO as a measure of the U.S. monetary base.