exam 2 intermed econ


1. Why GDP = National Income (Y)



Memorizable paragraph:


Gross Domestic Product (GDP) measures the total value of all final goods and services produced in an economy during a given period. At the same time, this production generates income for the factors of production—workers receive wages, landowners receive rent, lenders receive interest, and firms receive profits. Because every dollar spent on production becomes income for someone, the total value of output must equal total national income. Therefore, aggregate output (GDP) always equals national income (Y). In the graph of the market for aggregate goods and services, this equality is represented by the 45-degree line, where GDP equals income.





2. Components of GDP



Key formula


GDP = C + I + G + NX


Where:


  • C = Consumption (household spending)

  • I = Investment (business spending on capital and housing)

  • G = Government purchases

  • NX = Net exports (exports − imports)



Memorizable paragraph:


Aggregate output, or GDP, is made up of four components: consumption, investment, government spending, and net exports. Consumption represents household spending on goods and services. Investment includes business spending on capital goods and new housing construction. Government spending refers to purchases of goods and services by the government. Net exports equal exports minus imports and represent spending by foreign countries on domestically produced goods. Together, these components determine the total level of economic activity in the economy.





3. If G = 0 and NX = 0



Then:


GDP = C + I


Paragraph:


If government spending and net exports are assumed to be zero, the GDP identity simplifies to GDP = C + I. This means that total output in the economy is determined only by household consumption and business investment. In this simplified economy, households spend money on goods and services, while firms invest in capital and production. Without government spending or international trade, all economic activity comes from consumption and investment.





4. Components of National Income



Paragraph:


National income represents the total income earned by the factors of production in an economy. It includes wages and salaries paid to workers, rent earned by owners of land and property, interest received by lenders of capital, and profits earned by businesses. These incomes arise from the production of goods and services. Because every dollar of output generates income for someone, the sum of wages, rent, interest, and profits equals national income.





5. Aggregate Consumption Function



Formula:


C = A + BY


Where:


  • A = autonomous consumption

  • B = marginal propensity to consume (MPC)

  • Y = national income



Paragraph:


The aggregate consumption function describes the relationship between total consumption and national income. It is typically written as C = A + BY. Autonomous consumption (A) represents spending that occurs even when income is zero, while B represents the marginal propensity to consume, which is the fraction of additional income that households spend. As income increases, consumption rises according to the slope of the consumption function, which equals the marginal propensity to consume.





6. Y-Intercept and Slope



Paragraph:


In the graph of the aggregate consumption function, the Y-intercept represents autonomous consumption (A). This is the level of consumption that occurs even when income is zero. The slope of the line represents the marginal propensity to consume (MPC), which shows how much consumption increases when income rises by one unit. For example, if the MPC equals 0.6, households spend 60 cents of every additional dollar of income and save the remaining 40 cents.





7. Derive Why Savings = Investment



Steps:


  1. GDP identity:



Y = C + I


  1. Income is either consumed or saved:



Y = C + S


  1. Set them equal:



C + I = C + S


  1. Subtract C:



I = S


Paragraph:


Savings are identically equal to investment expenditures in the national income accounts. Starting with the GDP identity Y = C + I, national income equals consumption plus investment. Income can also be divided between consumption and saving, so Y = C + S. Since both equations equal Y, we set them equal to each other: C + I = C + S. Subtracting consumption from both sides leaves I = S. Therefore, in equilibrium, total savings in the economy must equal total investment.