Remember to mention the output gap when doing an essay that involves the business cycle. The output gap is the difference between demand and the economy’s capacity to supply. This is the difference between the ‘actual’ level of output (GDP) and the economy’s ‘potential’ level of output (potential GDP).
If the economy is running above capacity (GDP > potential GDP) the output gap is positive. Conversely, if the economy is running below its full capacity (GDP < potential GDP) the output gap will be negative.
Remember that ‘potential’ output is not an upper limit on the level of output. Rather, think of potential GDP as the economy’s efficient level of output. Running the economy below potential GDP is inefficient because there are some resources that are not employed. Running the economy above potential GDP is also inefficient because resources are over-utilised (eg, machinery is being made to work too hard causing it to wear out too quickly).
While it is efficient to have the economy running at potential, quite often it does not. Resources can be over- or under-utilised, which will translate into inflationary or disinflationary pressure (over-utilisation will push future inflation up, while under-utilisation pushes future inflation down).