The external interest rate effect:
Is the return from the implied forward rates (expected return) considered as the same as the market implied return from forward rates (unexpected return)?
For instance,
Implied Forward Rate (expected return) = 5%
Market implied return from forward rate = 5%
Actual realized return = 6%
Therefore, the unexpected return is actual realized return - market implied return from forward rate => 6% - 5% = 1%,
Actual return is expected return + unexpected return => 5% + 1% = 6%