The model reflects four periods or phases that create an arbitrary but pattern of hills and valleys.

The $,$ hase is a period in which RGDP is rising. The peak period is a temporary $-$ of RGDP$.$

The phase is a period of falling real gross domestic product. The trough is a temporary of RGDP$.$

Economists study the events of each phase of the business cycle to create forecasts for future events.

The natural rate of output is the long run GDP of an economy. When an economy is operating at a point where the actual adjusted short run GDP and the trend line or the economy is at the natural rate of output.

The market is where firms pay out wages to workers and households earn their incomes.

In the United States, the $.$ labor force is includes all men, women and children between the ages of $16$ and $65$ who are citizens or with legal residency to work, that are willing and able to sell the service of their labor in the market.

unemployment occurs because of the information required and time it takes for capable workers seeking employment.

unemployment happens when the qualifications of the available workers do not match the requirements needed for employment.