Demand-pull inflation is when aggregate demand exceeds the value of output (measured in constant prices) at full employment. The excess demand of goods and services cannot be met in real terms and therefore is met by rises in the prices of goods. Demand-pull inflation could be caused by:
Monetarist economists believe that "inflation is always and everywhere a monetary phenomenon in the sense that it can only be produced by a more rapid increase in the quantity of money than in output" as Friedman wrote in 1970.
The monetarist's theory is based upon the identity:
M x V = P x T
And thus this was turned into a theory by assuming that V and T are constant. Thus, we would obtain the formula
MV = PT