Investment demand function: Investment demand function is the relationship among rate of interest and investment demand. There is an inverse relationship among the rate of interest and investment demand.
High interest rate implies lower level of investment demand. It is since higher rate of interest is to be matched with uniformly higher marginal effectiveness of capital. MEC begins reducing as investment level is increased. Accordingly, investment demand would rise only corresponding to the lower level of MEC all along with lower level of rate of interest.