What Is the Multiplier Effect?

The multiplier effect refers to the proportional amount of increase in final income that results from an injection of spending. Alternatively, a multiplier effect can also work in reverse, showing a proportional decrease in income when spending falls. Generally, economists are usually the most interested in how capital infusions positively affect income. Most economists believe that capital infusions of any kind, whether it be at the governmental or corporate level, will have a broad snowball effect on various aspects of economic activity.


Multiplier Effect

Multiplier Effect Explained

Like its name, the multiplier effect involves a multiplier that provides a numerical value or estimate of an expected increase in income per dollar of investment. In general, the multiplier used in gauging the multiplier effect is calculated as follows:

Change in Income / Change in Spending

The multiplier effect can be seen in several different types of scenarios and used by a variety of different analysts when analyzing and estimating expectations for new capital investments.

For a basic example, assume a company makes a $100,000 investment of capital to expand its manufacturing facilities in order to produce more and sell more. After a year of full production with the new facilities, the company’s income increases by $200,000. When isolating the $200,000 and $100,000 for use in the multiplier effect the company’s multiplier would be 2 ($200,000/$100,000). This shows that for every $1 they invested, they earned an extra $2.

Key Takeaways

  • In general, the most basic multiplier used in gauging the multiplier effect is calculated as change in income / change in spending.
  • The multiplier effect can be used by companies or calculated on a larger scale with the use of GDP.
  • Economists may view the multiplier effect from several angles including usage of a calculation involving marginal propensity to consume.
  • The money supply multiplier is also another variation of a standard multiplier, using a money multiplier equation to analyze multiplier effects on the money supply.

Broader Economic Views

Many economists believe that new investments can go far beyond just the effects of a company’s income. Thus, depending on the type of investment, it may have widespread effects on the economy at large. A key tenet of Keynesian economic theory is the notion that economic activity can be easily influenced by investments causing more income for companies, more income for workers, more supply, and ultimately greater aggregate demand. Therefore, on a macro level, different types of economic multipliers can be used to help measure the impact that changes in investment have on the economy.

When looking at the economy at large, the multiplier would be the change in real GDP divided by the change in investments. Investments can include government spending, private investments, taxes, interest rates, and more.

When estimating the effects of $100,000 by the manufacturing company on the economy overall, the multiplier would be much smaller. For example, if GDP grew by $1 million, the multiplier effect of this investment would be 10 cents per dollar.

Some economists also like to factor in estimates for savings and consumption. This involves a slightly different type of multiplier. When looking at savings and consumption, economists might measure how much of the added economic income consumers are saving versus spending. If consumers save 20% of new income and spend 80% of new income then there marginal propensity to consume (MPC) is 0.8. Using an MPC multiplier, the equation is 1/(1-MPC). Therefore in this example, every new production dollar creates extra spending of $5 (1/(1-.8).

Money Supply Multiplier Effects

Economists and bankers often look at a multiplier effect from the perspective of banking and money supply. This multiplier is called the money supply multiplier or just the money multiplier. The money multiplier involves the reserve requirement set by the board of governors of the Federal Reserve System and it varies based on the total amount of liabilities held by a particular depository institution. The most recent Federal Reserve, reserve requirements require institutions with more than $124.2 million to have reserves of 10%.

In general, the money supply across the entire U.S. economy consists of multiple levels. The first level refers to all of the physical currency in circulation within an economy (usually M1). The next level adds the balances of short-term deposit accounts for a summation called M2.

When a customer makes a deposit into a short-term deposit account, the banking institution can lend one minus the reserve requirement to someone else. While the original depositor maintains ownership of the initial deposit, the funds created through lending are generated based on those funds. If a second borrower subsequently deposits funds received from the lending institution, this raises the value of money supply even though no additional physical currency actually exists to support the new amount.

Most economists view the money multiplier in terms of reserve dollars and that is what the money multiplier formula is based on. Theoretically, this leads to a money (supply) reserve multiplier formula of:

1/Reserve Requirement Ratio

When looking at banks with the highest required reserve requirement of 10%, their money supply reserve multiplier would be 10 (1/.10). This means every one dollar of reserves should have $10 in money supply deposits.

The money supply multiplier effect can be seen in a country's banking system. An increase in bank lending should translate to an expansion of a country's money supply. The size of the multiplier depends on the percentage of deposits that banks are required to hold as reserves. When the reserve requirement decreases the money supply reserve multiplier increases and vice versa.

If the reserve requirement is 10%, then the money supply reserve multiplier is 10 and the money supply should be 10 times reserves. When a reserve requirement is 10%, this also means that a bank can lend 90% of its deposits.

Looking at the example below provides some additional insight. 

Money Supply Multiplier Example
Money Supply Multiplier Example.

Looking at the money multiplier in terms of reserves helps best to understand the amount of expected money supply. When banks have a reserve requirement of 10%, there should be 10 times the total reserves in money supply. In this example, $651 equates to reserves of $65.13. If banks are efficiently using all of their deposits, lending out 90%, then reserves of $65 should result in money supply of $651. If banks are lending more than their reserve requirement allows their multiplier will be higher creating more money supply. If banks are lending less their multiplier will be lower and the money supply will also be lower. Moreover, when 10 banks were involved in creating total deposits of $651.32, these banks generated new money supply of $586.19 for a money supply increase of 90% of the deposits.