Milton Friedman makes the demand for money a function of the real per capital permanent income. in this study the demand function for money is stated as;M/NPP= r( YP/NP) δ
M = nominal stock of money N = population Yp = permanent income Pp = permanent prices
This latter version of the demand for money is not as different from the first version as it appears to be because the concept of permanent income is broad enough to include several variables used in the earlier version of the demand for money . permanent income is affected by yield on securities and human and non human wealth holdings.
According to Milton Friedman, on the basis of empirical evidence the demand for nominal cash balance is represented by the following equation.
M =(0.00323)(Yp/N)1.81 (NPp)
Where all the variables have the same definition as stated above except ,Yp which stands for the real permanent income . in the above form the equation expresses that ( assuming population and permanent prices to be constant ) a 1 per cent increase in real permanent income increase the de4mand for the nominal cash balances by 1.81 per cent. In other words, the Friedman equation for the demand for money indicates that the real permanent income elasticity for the demand for nominal cash balances is 1.81. according to Friedman the causal relationship runs from change in the money supply to change in income .