Final answer:
Total spending must be equal to total income in an economy because GDP measures what is spent on final sales of goods and services. Adjusting government spending levels and tax rates can help achieve full employment.
Step-by-step explanation:
When the macroeconomy is in equilibrium, it must be true that the aggregate expenditures in the economy are equal to the real GDP, because by definition, GDP is the measure of what is spent on final sales of goods and services in the economy. This is shown on a Keynesian cross diagram where aggregate expenditure and output are equal, which occurs along the 45-degree line.
For issues of policy, adjusting government spending levels or tax rates can help achieve the full employment level of output. The equilibrium level of output can be found mathematically by equating national income with aggregate expenditure.
Learn more about Macroeconomic equilibrium here: