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:

• Increases in general level of demand of goods and services. A rise in aggregate demand in a situation of nearly full employment will create excess demand in may individual markets, and prices will be bid upward. The rise in demand for goods and services will cause a rise in demand for factors and their prices will be bid upward as will. Thus, inflation in the pries of both consumer goods and factors of production is caused by a rise in aggregate demand.

• General shortage of goods and services. If there is a general shortage of commodities e.g. in times of disasters like earthquakes, floods or wars, the general level of prices will rise because of excess demand over supply.

• Government spending: Hyper-inflation certainly rises as a result of government action. Government may finance spending though budget deficits; either resorting to the printing press to print money with which to pay bills or, what amounts to the same thing, borrowing from the central bank for this purpose. Many economists believe that all inflation is caused by increases in money supply.

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