Demand is measured over a given time period.
It is determined by a number of factors including income, tastes and the price of complementary and substitute goods. Demand pull inflation - Occurs when aggregate demand exceeds aggregate supply. If there is an excess level of demand in the economy, this will tend to cause prices to rise. This type of inflation is called demand-pull inflation and is argued by Keynesians to be one of the main causes of inflation. Demerit goods - A product, such as alcohol, which consumers may overvalue but which the government believes may be harmful for consumers.