<Dd> r t = P 0 ⋅ Q t P t / P 0 ⋅ Q t − 1 P t − 1 − 1 (\ displaystyle r_ (t) = (\ frac (P_ (0) \ cdot Q_ (t)) (P_ (t))) / (\ frac (P_ (0) \ cdot Q_ (t - 1)) (P_ (t - 1))) - 1) </Dd> <Dl> <Dd> <Dl> <Dd> = P t − 1 ⋅ Q t P t ⋅ Q t − 1 − 1 (\ displaystyle = (\ frac (P_ (t - 1) \ cdot Q_ (t)) (P_ (t) \ cdot Q_ (t - 1))) - 1) </Dd> </Dl> </Dd> </Dl> <Dd> <Dl> <Dd> = P t − 1 ⋅ Q t P t ⋅ Q t − 1 − 1 (\ displaystyle = (\ frac (P_ (t - 1) \ cdot Q_ (t)) (P_ (t) \ cdot Q_ (t - 1))) - 1) </Dd> </Dl> </Dd> <Dl> <Dd> = P t − 1 ⋅ Q t P t ⋅ Q t − 1 − 1 (\ displaystyle = (\ frac (P_ (t - 1) \ cdot Q_ (t)) (P_ (t) \ cdot Q_ (t - 1))) - 1) </Dd> </Dl>

Explain why changes in money growth affect the nominal interest rate but not the real interest rate