An effect in economics in which an increase in spending produces an increase in national income and consumption greater than the initial amount spent. For example, if a corporation builds a factory, it will employ construction workers and their suppliers as well as those who work in the factory. Indirectly, the new factory will stimulate employment in laundries, restaurants, and service industries in the factory's vicinity.
Multiplier Effect
The expansion of a country's money supply that results from banks being able to lend. The size of the multiplier effect depends on the percentage of deposits that banks are required to hold on reserves. In other words, it is money used to create more money and calculated by dividing total bank deposits by the reserve requirement.
Investopedia Commentary
The multiplier effect depends on the set reserve requirement. So, to calculate the impact of the multiplier effect on the money supply, we start with the amount banks initially take in through deposits and divide by the reserve ratio. If, for example, the reserve requirement is 20%, for every $100 a customer deposits into a bank, $20 must be kept in reserve. However, the remaining $80 can be loaned out to other bank customers. This $80 is then deposited by these customers into another bank, which in turn must also keep 20%, or $16, in reserve but can lend out the remaining $64. This cycle continues - as more people deposit money and more banks continue lending it - until finally the $100 initially deposited creates a total of $500 ($100 / 0.2) in deposits. This creation of deposits is the multiplier effect.
The higher the reserve requirement, the tighter the money supply, which results in a lower multiplier effect for every dollar deposited. The lower the reserve requirement, the larger the money supply, which means more money is being created for every dollar deposited.
Related Links
The Federal Reserve (the Fed) Tutorial
Macroeconomic Analysis
See also: Federal Reserve System, Money Supply, Reserve Requirement, Velocity (of Money)