An individual holds B_0 dollars in a saving accountant at t=0 and earns continuously compounded interest at a nominal rate r. Therefore, the nominal value of his savings at time t is given B_t=e^rt. To find out the real value of his savings at each moment in time, we must divide by the price level. Assume the price level follows a geometric Brownian motion:
dP=pPdt+sPdz
where p is the expected rate of inflation and s is its volatility parameter
Let B_t/P_t be the real value of savings. Derive the law of motion for b using Ito’s Lemma. (Hint: you should obtain a law db=f (b)dt+ g(b)dz, where f and g are functions og just b for you to derive)
What is the individual’s expected real rate of return on his savings?
Calculate the expected real value of the individual’s savings at time t from the point of view of t=0, i.e E_¦(0@)[b_t]