DSE Economics | GDP and National Income Tutor Prep Guide

DSE Economics | GDP and National Income Tutor Prep Guide | Expenditure Approach

2026-11-01

Tutor lesson-prep guides · Secondary Economics

Students can recite GDP equals C plus I plus G plus net exports, but the moment a question separates domestic exports from re-exports they scramble, and they cannot say why imports are subtracted. They memorised a formula without the border that defines it. This lesson starts from that border.

Objectives — Students can: (1) compute GDP by the expenditure approach and justify each term; (2) convert nominal growth to real growth with the deflator; (3) compute GDP per capita and state its limits; (4) name three reasons GDP is an imperfect welfare measure.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Circular flow	flows between firms and households	expenditure equals income equals output
Domestic versus national	resident producing units	domestic product versus national income
Index numbers	what a deflator means	nominal to real needs division

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Draw the border	only domestic production counts	imports are not domestic output
8-22 min	Four spending terms	C, I, G, net exports	gives 2150
22-32 min	Domestic versus national	add NFIA for GNP	2110
32-44 min	Nominal versus real	use the deflator	real growth 3.22 percent
44-54 min	Per capita and limits	divide by population	286,667 per head
54-60 min	Exit check	collect and mark	independent

03 Teaching script (read it out)

Scene 1: First move: ask whether the spending is domestic output, then write the formula

GDP is the market value of final goods and services produced within an economy in a period. Household consumption of 1200, investment of 450 and government spending of 300 are all domestic output. Exports of 2100 are domestic output sold abroad, so they are added. Imports of 1900 were produced abroad and are already inside C, I and G, so they are subtracted.
GDP comes to 2150. Ask: why subtract imports rather than add them? (Because consumption and investment already include imported goods.)

Task: classify five transactions as inside or outside GDP.

Scene 2: Domestic versus national: NFIA is the only dividing line

GDP counts production inside the border, GNP counts production by residents. Income residents earn abroad is added and income foreigners earn here is subtracted; together they form net factor income from abroad. Here NFIA is -40, so GNP is 2150 plus (-40), which is 2110.
Students assume GDP always exceeds GNP, but large inward investment makes NFIA negative and GNP smaller, which is exactly Hong Kong. Reminder: re-export values are excluded from GDP; only the trading margin counts. Ask: a domestic helper working in Hong Kong earns wages counted in which GDP? (Hong Kong, because production happens here.)

Scene 3: Nominal, real and per capita: divide one layer at a time

Nominal GDP grew 5.8 percent while the deflator rose 2.5 percent, so real growth is (1+0.058) divided by (1+0.025) minus one, which is 3.22 percent. Subtracting to get 3.3 percent is only a rough estimate; the ratio is the exam answer.
GDP per capita is 2150 hundred million divided by 7.5 million, about 286,667. Comparing two economies per capita has three limits: exchange rates, purchasing power and income distribution.

Task: if population grows 2 percent, what happens to per capita growth? (Real growth minus population growth.)

04 Question types and worked steps

Type	Example	Steps	Answer
Expenditure approach	given C, I, G, X, M	C plus I plus G plus net exports	2150
GDP versus GNP	given NFIA	GDP plus NFIA	2110
Real growth	given nominal growth and deflator	ratio method	3.22 percent
Evaluation	is GDP welfare	list three limits	distribution, environment, unpaid work

Sanity check (teach this): GDP is positive; a negative answer means the net export sign is reversed. Net exports can be negative in a deficit, but GDP does not turn negative. Real growth is below nominal growth whenever the deflator rises. Per capita figures are in dollars while totals are in hundred millions, a factor of a million apart. GNP and GDP should not differ by more than about a tenth, or NFIA is in the wrong unit.

05 Independent practice (3 questions)

Question	Answer	What to watch
GDP with C 1200, I 450, G 300, X 2100, M 1900	2150	C plus I plus G plus net exports
GNP when NFIA is -40	2110	2150 minus 40
Real growth with nominal 5.8 and deflator 2.5	3.22 percent	ratio method

06 Common mistakes and what to say

Mistake	Student writes	Say this
Adding instead of subtracting imports	answers 2550	Imports are foreign output already inside consumption, so they are subtracted.
Treating GDP and GNP as one	claims GDP always exceeds GNP	GDP counts inside the border, GNP counts residents, and Hong Kong has negative NFIA.
Subtracting for real growth and stopping	answers 3.3 percent	The ratio method is the full-mark answer; subtraction is an estimate.
Wrong per capita unit	answers 28.7 dollars	Totals are in hundred millions and population in millions, so the result is in dollars.

07 Homework (paper, section and question numbers)

Secondary economics chapter index — questions 5 and 8
Prep guide directory — other chapters in this subject
DSE economics practice papers — national income set, questions 1-7

08 Exit check (last 5 minutes)

Question	Answer	Decision
GDP with C 1200, I 450, G 300, X 2100, M 1900	2150	three correct means move to inflation
The GDP and GNP dividing line	domestic versus residents	one wrong means reteach next lesson
Two limits of GDP as welfare	distribution and unpaid work	two wrong means restart act one

09 Tutor FAQ

Why are re-exports excluded from GDP?

The goods were not produced locally, so only the trading margin earned here is counted.

Is volunteer work in GDP?

No, because there is no market transaction, which is one reason GDP understates welfare.

How does the deflator differ from the consumer price index?

The deflator covers all domestic output while the CPI covers only a household basket.

Find a tutor — free Tutor Registration →

A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.