Demand, the Rental Rate, and Economic RentWhen the supply of a factor of production is fixed, the rental rate is determined by the level of demand. For example, if the demand curve for land were D1, the annual rental rate would be zero. If the demand curve were D2, the rental rate would be $1,000 per acre. And if the demand curve were D3, the rental rate would be $4,000 per acre. The shaded area of the graph represents the economic rent of $4,000 × 512 = $2,480,000 that exists when the rental rate is $4,000 per acre.