What is Fisher Effect ( Definition, formula )

What Is the Fisher Effect?

The economist Irving Fisher constructed a theory which is now referred to as the Fisher Effect, which depicts the relationship which is following between inflation and both the interest rates which are real and nominal interest rates. Here, the fisher states that the real rate of interest is equal to or derived as by subtracting the nominal interest rate with the expected inflation rate. Therefore, because of this relation, a change in the real rate of interest is due to the change in nominal rates.

So, we can say that the Fisher Effect is an economics theory dealing with the relationship between inflation and interest, where we are referring to the nominal as well as the real rate of interest prevailing.

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Nominal Interest Rates And Real Interest Rates:

  • Nominal interest rates: The Nominal interest rates shows us the monetary return which a specific person gets when he capitalizes his money in the business.
  • Real interest rate: The real rate of interest shows us the purchasing power of the company.

Here, the nominal rate of interest is the actual rate of interest that shows the growth of money over a period of time or the growth of the money, where as the real rate of interest tells us about the procuring supremacy of the borrowed money when it cultivates with time.

Fisher Effect Equation:

The fisher effect equation depicts or tells us the existing relationship of inflation and both the interest rates. Therefore, according to the Fisher relation equation, the nominal rate of interest is equivalent to the sum of the real rate of interest and the inflation, and this relationship can be depicted with the following equation:

i ≈ r + Pi

In the following fisher equation,

  • i = the nominal rate of interest
  • r = the real rate of interest, and the
  • Pi = the inflation or the expected inflation rate

Or it can also be depicted by the following equation:

I = r + πe


  • r refers to real interest rate,
  • i refers to nominal interest rate, and
  • πe refers to expected inflation.

The Fisher Equation has its usage in the economics as well as finance field, where it tells us about the investors or lenders demand, purchasing power of the company, growth of the company or the business, profitability, etc. Moreover, fisher effect in international finance or trading of currencies and the demand for money in the market is also analysed by the equation of fisher.

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How To Calculate The Fisher Effect?

The formal used for calculation is as follows:

(1 + nominal interest rate) = (1 + real interest rate) * (1 + inflation rate)

The formula In mathematical notation, can be written down as:

(1 + i) = (1 + r) * (1 + Pi)

Where the words I, r, Pi stands for:

  • i = the nominal interest rate
  • r = the real interest rate
  • Pi = the inflation rate

So, we can derive out the formula of fisher as follows:

i ≈ r + Pi

Fisher Equation Example 1:

A portfolio earned a return of 1.75 Percent. And the inflation rate for last year was around 8 Percent. And you need to find out the real return that you have earned from the portfolio.

So, to find the real rate of return, we have used the fisher effect equation, which is as

(1 + i) = (1 + r) (1 + π)

This equation can also be written down as follows, by rearranging the equation,

r = (1 + i) / (1 + π) – 1

And, now putting the values in the equation as,

I = 1.75 Percent

Π = 8 Percent

We get, r = (1 +1.75 Percent) / (1 + 8 Percent) – 1

= 6.25 Percent

So, you will earn a return of 6.25 percent on your investments.

Fisher Equation Example 2:

When the real rate of interest is 3.6 Percent and the Inflation Rate is 2.2 percent, then what will be the Nominal Interest Rate?

In order to calculate the Nominal Interest Rate using fisher equation, we will use the fisher effect formula which says that,

Nominal Interest Rate = Real Interest Rate + Inflation

And putting down the values in the above formula as,

Real Interest Rate = 3.6 Percent and Inflation = 2.2 Percent

we get, the equation as follows,

Nominal Interest Rate = 3.6 Percent+ 2.2 Percent= 5.80 Percent

Therefore, the nominal interest rate is 5.80 Percent, which is calculated with the help of fisher formula.

What Is The International Fisher Effect (IFE)?

The international fisher effect suggests that the present and future risk-free nominal interest rates instead of using or showing the relationship about the pure inflation. The fisher has extended is usage to forex trading and to investigation. So, therefore, we use it to forecast and recognize the current as well as the upcoming spot currency values and their movements in the market.

Here, international fisher effect formula works on the following formula or equation:

RR nominal​=(1+RRreal​) ∗ (1+inflation rate)


  • RR nominal​ refers to the Nominal rate of return
  • RR real​ refers to the real rate of return​

The Fisher Effect Diagram:

The fisher effect diagram shown above depicts the relation between the real rate of interest and inflation. As, I is the line of nominal interest rate, and π is the inflation that keeps on changing. So, the horizontal line shows us or represents the real rate of interest. And the point where the nominal rate of interest intersects the real rate of interest is the point where i=r or both the real and nominal rate of interest is equal.

Here, on the vertical axis is the nominal interest rate, and on the horizontal axis is the rate of inflation. Whereas, line A in the figure above, shows us the monetary policy or the supply of money in the market. And the dotted line B displays the relationship between the nominal interest rate and the inflation rates in the given fisher’s diagram. And we have assumed real interest rate to be 2 Percent.

The point E in the diagram is the equilibrium point where the real rate of interest is equal to 2 Percent, which is the equilibrium rate in the long run or where the nominal rate of interest is equal to the real rate of interest.

The Fisher Effect graph:

When the Demand and supply were at expected inflation of 0 Percent Then the nominal interest rate was 4 Percent and with the rise of demand and supply of loanable fund at 10{367c01af22dc6c3a8611ff25983b0f0a247ed9fc1c45fd9103ad49b47a0c5f39} the inflation rate has also increased.

Here, in the above graph of fisher, we can see that with the rise in supply and demand or with the rise of inflation the nominal rate of interest also upsurges. So, there exists an inverse relationship between the nominal rate of interest and the inflation.

Advantages Of The Fisher Effect

  • It depicts a clear difference or picture of the nominal rate of interest as well as the real interest rate.
  • It donates towards the sustainable development of the economy.

Disadvantages Of The Fisher Effect

  • It can result in the rise of interest rates by reducing the nominal interest rates.
  • The central banks can increase the real rate of interest due to the continuous rise in prices.