# What Is the Multiplier Effect? Formula and Example

## What Is the Multiplier Effect?

The multiplier effect is an economic term, referring to the proportional amount of increase, or decrease, in final income that results from an injection, or withdrawal, of capital. In effect, Multipliers effects measure the impact that a change in economic activity—like investment or spending—will have on the total economic output of something. This amplified effect is known as the multiplier.

### Key Takeaways

• The multiplier effect is the proportional amount of increase or decrease in final income that results from an injection or withdrawal of spending.
• The most basic multiplier used in gauging the multiplier effect is calculated as the change in income divided by the change in spending and is used by companies to assess investment efficiency.
• The money supply multiplier, or just the money multiplier, looks at a multiplier effect from the perspective of banking and money supply.
• The money multiplier is a key concept in modern fractional reserve banking.
• Other multipliers include the deposit multiplier, fiscal multiplier, equity multiplier, and earnings multiplier.
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## Understanding the Multiplier Effect

Generally, economists are most interested in how infusions of capital positively affect income or growth. Many economists believe that capital investments of any kind—whether it be at the governmental or corporate level—will have a broad snowball effect on various aspects of economic activity.

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

\begin{aligned}\text{Multiplier}=\frac{\text{Change in Income}}{\text{Change in Spending}}\end{aligned}

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.

## Example of the Multiplier Effect

For 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 production with the new facilities operating at maximum capacity, the company’s income increases by$200,000. This means that the multiplier effect was 2 ($200,000 /$100,000). Simply put, every $1 of investment produced an extra$2 of income.

## The Keynesian Multiplier

Many economists believe that new investments can go far beyond just the effects of a single 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 that of the multiplier, 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.

Essentially, the Keynesian multiplier is a theory that states the economy will flourish the more the government spends, and the net effect is greater than the exact dollar amount spent. Different types of economic multipliers can be used to help measure the exact impact that changes in investment have on the economy.

For example, when looking at a national economy overall, the multiplier would be the change in real GDP divided by the change in investments, government spending, changes in income brought about by changes in disposable income through tax policy, or changes in investment spending resulting from monetary policy via changes in interest rates.

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 income consumers are saving versus spending. If consumers save 20% of new income and spend 80% of new income, then their marginal propensity to consume (MPC) is 0.8. Using an MPC multiplier, the equation would be:

\begin{aligned}&\text{MPC Multiplier}=\frac{1}{1-\text{MPC}}=\frac{1}{1-0.8}=5\\&\textbf{where:}\\&\text{MPC}=\text{Marginal propensity to consume}\end{aligned}

Therefore, in this example, every new production dollar creates extra spending of $5. ## Money Supply Multiplier Effect Economists and bankers often look at a multiplier effect from the perspective of banking and a nation's 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 Federal Reserve, and it varies based on the total amount of liabilities held by a particular depository institution. In general, there are multiple levels of money supply across the entire U.S. economy. The most familiar ones are: • The first level, dubbed M1, refers to all of the physical currency in circulation within an economy. • The next level, called M2, adds the balances of short-term deposit accounts for a summation. 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 their 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 the money supply even though no additional physical currency actually exists to support the new amount. 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. Back in 2020, prior to the COVID-19 pandemic, the Fed mandated that institutions with more than$127.5 million have reserves of 10% of their total deposits. However, as the pandemic sparked an economic crisis, the Fed took a dramatic step: On Mar. 26, 2020, it reduced the reserve ratio to 0%—essentially, eliminating these requirements entirely to free up liquidity.

### Money Supply Reserve Multiplier

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:

\begin{aligned}&\text{MSRM}=\frac{1}{\text{RRR}}\\&\textbf{where:}\\&\text{MSRM}=\text{Money supply reserve multiplier}\\&\text{RRR}=\text{Reserve requirement ratio}\end{aligned}

## Is a High Multiplier Good?

Each type of multiplier is individually defined and often has different metrics that define success. Very broadly speaking, most multipliers that are high indicate higher economic output or growth. For example, a higher money multiplier by banks often signals that currency is being cycled through an economy more times and more efficiently, often leading to greater economic growth.

## What Causes the Multiplier Effect?

Some multiplier effects are simply the product of metric analysis as one number is compared to another. In other cases, the multiplier effect is a product of public policy or corporate governance. For example, the government may establish boundaries on how many times a deposit may be cycled through an economy. These regulations are often in place to restrict the multiplier effect; otherwise, financial institutions may become encumbered with too much risk.

## The Bottom Line

Multiplier effects describe how small changes in financial resources (such as the money supply or bank deposits) can be amplified through modern economic processes, sometimes to great effect. John Maynard Keynes was among the first to describe how governments can use multipliers to stimulate economic growth through spending. In fractional reserve banking, the money multiplier (or deposit multiplier) effect shows how banks can re-lend a portion of the deposits on-hand to increase the amount of money in the economy. In this way, commercial banks have a large degree of influence on economic outcomes.

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1. Federal Reserve Board. "What Is the Money Supply? Is It Important?"

2. Federal Reserve Board. "Reserve Requirements."

3. International Monetary Fund. "What Is Keynesian Economics?"