Final answer:
The ex post real interest rate is greater than the ex ante real interest rate when the actual inflation is less than expected, leading to a higher than expected real cost of borrowing.
Step-by-step explanation:
The ex post real interest rate will be greater than the ex ante real interest rate when the actual rate of inflation is less than the expected rate of inflation. When inflation is lower than anticipated, the real interest rate effectively increases beyond what was expected at the time the loan was issued. For example, if the nominal interest rate is 7% and the expected inflation was 3%, borrowers would anticipate a 4% real interest rate. However, if there is an unexpected deflation of 2%, the real interest rate would rise to 9%, which can hurt borrowers by increasing the real cost of their debts and can potentially lead to widespread defaults and a decrease in aggregate demand, risking a recession.