ECON1002 · Introductory Macroeconomics
Measuring Output: GDP
GDP is the market value of all final goods and services produced within a country in a given period, and Week 1 builds it three equivalent ways — by expenditure (C + I + G + X − M), by value-added, and by income. You then separate nominal from real GDP using the GDP deflator, distinguish GDP from GNI, and weigh GDP's limits as a measure of well-being.
It is examined as MCQ number-work in the IST and the final's Section A: most questions hand you components and ask you to recover a missing one (often investment), or give a price-quantity table and ask for nominal-GDP growth, real-GDP growth and the deflator.
What this chapter covers
- 011. What GDP is: market value of FINAL goods & services, within a territory, over a period (avoid double counting)
- 022. Expenditure approach: GDP = C + I + G + X − M
- 033. Value-added approach: Σ(firm revenue − cost of intermediate inputs)
- 044. Income approach: GDP = Compensation of employees + Gross operating surplus + Net indirect taxes
- 055. GDP vs GNI: GNI = GDP + net factor income from non-residents
- 066. Nominal vs real GDP: Nominal = Σ(P×Q) at current prices; Real holds prices at a base year
- 077. GDP deflator = (Nominal GDP / Real GDP) × 100; chain-volume real GDP
- 088. Limits of GDP: ignores leisure, non-market work, the environment, inequality; alternatives (HDI, Better Life Index)
GDP three approaches — recover missing investment
- 1 markUse the income approach to find total GDP: GDP = Compensation of employees + Gross operating surplus + Net indirect taxes = 540 + 300 + 60 = 1000.
- 1 markUse the expenditure approach to back out I: GDP = C + I + G + NX ⇒ I = GDP − (C + G + NX) = 1000 − (620 + 180 + (−10)) = 1000 − 790 = 210.
Key terms
- Final vs intermediate goods
- Final goods are sold to the end user and counted in GDP; intermediate goods are inputs resold or transformed by another firm and are excluded, because their value is already embedded in the final good. Counting both would double-count.
- Expenditure approach (C + I + G + X − M)
- Adds all spending on final output: household consumption C, business investment I, government spending G, and net exports X − M (imports are subtracted because they are produced abroad).
- Income approach
- Sums the incomes generated in production: compensation of employees (labour income) + gross operating surplus (capital income) + net indirect taxes (indirect taxes − subsidies). In principle it equals the expenditure total.
- GNI vs GDP
- GDP measures production located within the country; Gross National Income (GNI) measures income earned by residents, GDP + net factor income received from abroad. They differ when a country has large foreign-owned production or residents earning income overseas.
- GDP deflator
- A broad price index defined as (Nominal GDP / Real GDP) × 100. Unlike the CPI it covers all GDP components and uses current-period quantities, so it captures economy-wide rather than household-basket inflation.
- Chain-volume measure
- A way of computing real GDP that updates the base year each period and links the results into a chain, reducing the bias from using fixed, increasingly out-of-date prices.
Measuring Output: GDP FAQ
How is GDP examined in ECON1002?
As MCQ calculation. The classic versions give you several expenditure or income components and ask you to recover a missing one (very often investment), or hand you a price-quantity table and ask for nominal-GDP growth, real-GDP growth and the GDP deflator. Showing you can move between the expenditure and income approaches, and between nominal and real, is the whole skill.
What is the difference between real GDP and the CPI?
Both adjust for prices but in opposite ways. Real GDP fixes PRICES at a base year and lets quantities vary, so it measures the volume of output. The CPI fixes QUANTITIES (a fixed basket) at the base year and lets prices vary, so it measures the cost of living. Because they hold different things constant, they give different inflation numbers from the same data.
Why do we subtract imports in GDP = C + I + G + X − M?
Imports are subtracted because C, I and G already include spending on imported goods, but those goods were produced overseas, not domestically. Subtracting M removes that foreign-produced portion so GDP only counts production within the country. This is why a rise in imports, holding everything else fixed, lowers measured GDP.
Why is GDP a poor measure of well-being?
GDP counts market production but ignores leisure, household and volunteer work, the underground economy, environmental damage and the distribution of income — and it can rise for 'bad' reasons (rebuilding after a disaster). It is a useful production thermometer but not a welfare index, which is why economists also look at HDI, the OECD Better Life Index and per-capita real GDP alongside it.
Exam move
Drill the two directions until they are automatic: given components, recover a missing one (income approach to get total GDP, then expenditure approach to solve for I); and given a price-quantity table, compute nominal GDP (current P×Q), real GDP (base-year prices × current quantities) and the deflator. Build a tiny worked table with columns for price, quantity and value so you never confuse which year's prices to hold fixed. Watch signs ruthlessly — net exports are often negative, and subtracting a negative adds it back. Finally, memorise the one-line distinction 'real GDP fixes prices, CPI fixes the basket', because a single MCQ almost always rewards it.
