
5-4 INTRODUCTION TO CAPITAL BUDGETING
v-1.1 v.05/13/94
p.01/14/00
Adjusting for Inflation
Relationship
between
nominal, real,
and inflation
rates
Inflation is one of the most influential factors in the determination
of nominal interest rates. You may recall that when we discussed
inflation in Unit Two, we said that the quoted (nominal) interest rate is
equal to the risk-free real interest rate plus an inflation premium. A
more precise formula should be used to find the effective interest rate
when making adjustments for longer-term securities or in
environments of high inflation. The relationship between nominal,
real, and inflation rates can be calculated with this formula:
R
R
= [ (1 + R
N
) / (1 + h) ] - 1
Where:
R
R
= Real interest or real discount rate
R
N
= Nominal interest or discount rate
h = Expected inflation rate
Effective
interest rate
after adjusting
for inflation
Let's look at an example to see how we apply the formula to find
out the effective interest rate on an investment after adjusting for
inflation.
Suppose that a Central Treasury Bank issues one-year bonds at a
nominal interest rate of 25% p.a. Economists expect that the average
inflation for the coming year will be 14%. What is the real interest
rate that an investor can expect to earn by buying the bonds? We use
the values R
N
= 0.25 and h = 0.14.
R
R
= [ (1 + R
N
) / (1 + h) ] - 1
R
R
= [ (1 + 0.25) / (1 + 0.14) ] - 1
R
R
= [ (1.25) / (1.14) ] - 1
R
R
= [ 1.0965 ] - 1
R
R
= 0.0965 or 9.65%
This means that although the stated interest rate on the bonds is
25%, after adjusting for inflation, an investor actually earns only
9.65% on the investment. The difference between the two rates
represents the loss of purchasing power resulting from inflation. As
we mentioned before, this concept is particularly important in
economies experiencing high levels of inflation.