Skip to content

IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Allowing for inflation

An investment earns a nominal effective annual return of 8% while the price index rises by 5% each year. What is the real effective annual rate of return, to two decimal places?

The real rate of return is 2.86%. It comes from dividing one plus the nominal rate by one plus the inflation rate, 1.08/1.05, and subtracting one. Simply subtracting 5% from 8% to get 3% ignores compounding and overstates the real return.

  1. A2.86%Correct
  2. B3.00%
  3. C2.76%
  4. D13.40%
  5. 2.50%

Explanation

The real rate satisfies (1+i) = (1+r)(1+e), so r = 1.08/1.05 - 1 = 0.028571, or 2.86%. The simple difference 8% - 5% = 3.00% ignores the compounding interaction between interest and inflation, so it is wrong.

Did you get it right without looking?

One question tells you little. A timed set on Allowing for inflation shows your real accuracy, how long you take and where you lose marks.

More Allowing for inflation questions