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  • Writer's picturePeak Frameworks Team

What is the Fisher Equation? Explanation and Examples in Finance

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What is the Fisher Equation?

The Fisher Equation, named after the economist Irving Fisher, delineates the relationship between nominal interest rates, real interest rates, and inflation.

The foundational formula of the Fisher Equation is:

fisher equation formula


i = nominal interest rate

r = real interest rate

π = inflation rate

The Fisher Equation becomes important when you are looking to invest in assets or understand monetary policy decisions made by central banks.

Fisher Equation
Source: Slideshare

In the context of this discourse, we shall consider a hypothetical scenario:

Jenny is a schoolteacher. Every month, she saves a little bit of her salary. She's heard about people making their savings grow by investing. Jenny isn't a finance guru, but she's smart and wants to make an informed decision.

One day, her bank offers her a special savings account. If she locks her money for a year, they promise to give her 5% interest by the end of the year. It sounds tempting. But Jenny remembers hearing something about inflation and wants to consider it.

Inflation is a bit like an invisible thief. Imagine you can buy a basket of your favorite fruits for $100 today. But if next year, due to inflation, the same basket costs $103, then the value of your $100 has effectively decreased.

Jenny learns that the predicted inflation for the next year is 3%. Now, she's confused. If her money grows by 5% in the bank but inflation is 3%, how much is she really benefiting?

This is where the Fisher equation helps, even if Jenny doesn't know its name or the formula. In layman's terms, it helps Jenny subtract that sneaky inflation from her bank's offered interest to find out her real gain.

Inflation Factors that Affect Cost of Living
Source: Investopedia

Doing the simple math, her real gain would be:

Interest from the bank (5%) - Inflation (3%) = Real gain (2%)

So, in reality, Jenny's savings will only grow by 2% in terms of actual buying power.

By understanding this, Jenny can decide if a 2% real gain is good enough for her or if she should look for a better investment opportunity.

Practical Implications of the Fisher Equation

By understanding this equation, finance professionals can deduce how a given inflation rate can impact both the real and nominal interest rates.

For instance, if we consider the European Central Bank's policy decisions after the 2008 financial crisis, one can see the practical application of the Fisher Equation.

In an environment of low inflation or deflation, the nominal interest rate can be significantly lower than the real interest rate, as demonstrated in this analysis.

Fisher Effect and Its Relevance

According to the Fisher Effect, if expected inflation changes, it can have an effect on the nominal interest rate but not on the real interest rate. Think about what the Federal Reserve did when people thought inflation would rise over the past ten years.

We can see the Fisher Effect at work by looking at these responses. The Federal Reserve changed nominal rates as inflation expectations rose so that the real interest rate would stay stable.

Application in Modern Finance

The Fisher Equation's insights are valuable for a range of financial professionals:

Private Equity Professionals

When assessing the value of potential investments or predicting future cash flows, understanding the interplay of inflation and interest rates is crucial.

For example, when KKR & Co. Inc. made significant investments in European markets during inflationary periods, knowledge of real versus nominal rates likely influenced their decision-making.

Investment Bankers

For those structuring deals or assessing company valuations, the Fisher Equation can guide interest rate expectations, which in turn can influence discount rates and other valuation metrics.

A case in point is the 2015 M&A boom in the U.S. where inflation and its projected trajectory significantly influenced deal structures and valuations.

Corporate Finance Professionals

CFOs and finance teams, especially in multinational corporations, must understand the Fisher Equation to make informed decisions about capital structure, especially concerning debt. An insightful read on this is available here.

Common Misconceptions and Mistakes

As with many financial tools, the Fisher Equation is not immune to misinterpretations. One prevalent myth is that a rise in inflation will always lead to a proportional increase in nominal interest rates.

In reality, central bank policies, market expectations, and other factors can often result in non-linear adjustments.

Case Studies: Real-life Application of the Fisher Equation

Post-2008 European Financial Crisis

During this period, many European countries experienced negative inflation (deflation). The Fisher Equation would imply negative nominal interest rates when real rates were positive. Indeed, some central banks implemented negative interest rate policies, as documented here.

U.S. Monetary Policy in the 2010s

The Federal Reserve, grappling with recovering from the Great Recession and maintaining economic growth, had to balance nominal rates and inflation expectations. By leveraging the Fisher Equation, the Fed ensured that real interest rates promoted economic growth without letting inflation run too hot.


The Fisher Equation, while seemingly simple, offers profound insights into the interrelationship between interest rates and inflation. For finance professionals, whether in private equity, investment banking, or corporate finance, grasping its nuances can significantly enhance decision-making efficacy.


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