DSE Geography | Population and Migration Lesson-Prep Guide (Tutor Edition)

DSE Geography | Population and Migration Lesson-Prep Guide (Tutor Edition) | Growth Rates and Dependency

2026-11-02

Tutor lesson-prep guides · Secondary Geography

Students read a pyramid by height alone and cannot say which band has to be supported. This lesson turns the shape into a ratio, then uses push and pull to explain the arrows.

Objectives — Students can: (1) compute natural increase and doubling time from birth and death rates; (2) compute the dependency ratio from a pyramid and tell expansive from constrictive; (3) explain rural-urban migration with push-pull factors and give two-sided impacts.

01 Prerequisites (3-minute check)

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

Skill	Quick check	Pass mark
Per thousand	What is 12 per thousand as a percentage	1.2%
Percentages	Ratio equals part over whole times 100	Same units throughout
Pyramids	What the two axes show	Population and age cohort

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-10 min	Three rates	Birth, death, natural increase	Students compute once
10-24 min	Doubling	Rule of 70 and its misuse	Get 140 years
24-38 min	Structure	Pyramid shape and dependency	Get 45.8%
38-50 min	Migration	Push, pull, barriers, impacts	Source and destination
50-56 min	Answer format	Factor, mechanism, consequence	Rewrite one answer
56-60 min	Exit check	Three questions marked on the spot	Independent work

03 Teaching script (read it out)

Scene 1: Natural increase: subtract two rates per thousand

Birth rate 12 per thousand, death rate 7 per thousand, so natural increase is (12 minus 7) divided by 1000 = 0.005, which is 0.5%.
Doubling time by the rule of 70: 70 divided by 0.5 gives 140 years. The rule is an approximation and overstates time at high growth.
Natural increase excludes migration; total change equals natural increase plus net migration.

Ask the student: if the death rate falls to 3 per thousand, what are the growth rate and doubling time (0.9%, about 78 years).

Scene 2: Structure: the dependency ratio is about load

With 0.9 million aged 0-14, 1.3 million aged 65 and over, and 4.8 million aged 15-64: ratio = (2.2 divided by 4.8) times 100 = 45.8%.
That means roughly 46 dependants per 100 people of working age. A narrow base with a wide top means an ageing population; a wide base means high fertility.

Warn: the denominator is the 15-64 band, never the total population.

Scene 3: Migration: push, pull and two-sided impacts

Push: unemployment, low wages, hazards, political instability. Pull: jobs, education and health care, family reunion, freedom.
Barriers between them: border controls, language, moving costs, visas.
Impacts must be split: the source may lose labour but gain remittances; the destination gains labour but faces pressure on housing and services.

Ask the student: which type of migration is Hong Kong importing domestic helpers (international, temporary, economically driven).

04 Question types and worked steps

Type	Example	Steps	Answer
Calculation	Natural increase	(Birth minus death) divided by 1000	0.5%
Calculation	Doubling time	70 divided by the percentage rate	140 years
Calculation	Dependency ratio	(Young plus old) over working age times 100	45.8%
Essay	Migration impacts	Source and destination, positive and negative	One line per cell

Sanity check (teach this): Natural increase is the difference of two rates per thousand divided by 1000, never the raw 5%. A dependency ratio above roughly 100% usually means the total population was used as the denominator. Doubling time moves inversely with the growth rate.

05 Independent practice (3 questions)

Question	Answer	What to watch
Natural increase at 12 and 7 per thousand	0.5%	Divide by 1000
Doubling time at 0.5%	about 140 years	Rule of 70
Dependency ratio for 0.9, 1.3 and 4.8 million	45.8%	Denominator is working age

06 Common mistakes and what to say

Mistake	Student writes	Say this
Writing 5% growth	Answers 12 minus 7 as 5%	“Per thousand first: 5 per thousand is 0.5%.”
Using total population as the denominator	Gets 31%	“The denominator is always the 15-64 band.”
Multiplying for doubling time	Answers 350 years	“70 divided by the rate, not multiplied.”
One-sided migration impacts	Only lists gains at the destination	“Write source and destination, positive and negative.”

07 Homework (paper, section and question numbers)

Secondary Geography chapter index (includes this chapter) — Independent practice questions 1 to 3 on this page
DSE lesson-prep overview and course map — All subject chapters

08 Exit check (last 5 minutes)

Question	Answer	Decision
Growth at 12 and 7 per thousand	0.5%	Three correct means move on
Denominator of the dependency ratio	Population aged 15-64	One wrong means re-teach ratios
How many sides in migration impacts	Source and destination	Two wrong means replay act three

09 Tutor FAQ

Is the rule of 70 exact?

It is close at low growth and overstates time above about 3%.

How many pyramid shapes are there?

Three main types: expansive, stationary and constrictive.

Why is Hong Kong ageing?

Sustained low fertility plus longer life expectancy; migration only partly offsets it.

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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.