Cumulative Amount of 16 Investment Having this Real Interest Rate () and Rate of Return or Higher, 14 Expected Rate of Return (r) Billions per Year 16% $ 0 Investment 14 5 10 demand 12 10 and real interest rate, i (percents) Expected rate of return, r, curve 10 15 8 20 6 25 ONAOOO 30 35 40 2 ID O 5 10 15 20 25 30 35 40 Investment (billions of dollars)