Lecture 26: Population structure

Question 1

Describe the main source of population (health) data

Answer 1

The Census
- Traditionally used enumeration officers to contact individual households in meshblocks : 100 ppl
Asked age, ethnicity , income, education
- 2018 census is online

Question 2

Why do we need population related data

Answer 2

Measuring trends:
Comorbidities, all cause mortality, births, migration

Used by epidemiologists as a DENOMINATOR to find some deficit measures:
unemployment, crime, health service utilisation, voting trends, education

Question 3

What is a strength of the Census

Answer 3

Can break down the data into any category/combos of different identifiers to determine the composition of the population.

Question 4

What is the Estimated Resident population as a source of data/ denominator

Answer 4

Census based info estimate of all people who usually live in NZ at a given rate from StatsNZ. It will not typically break down by ethnic

Question 5

What is Vital events data and what denominator is it providing

Answer 5

Births, Deaths, Marriages which is maintained by Dep of Internal affairs but Stats NZ prepares reports. - Could be useful to gauge immunity
-more objective

Question 6

What is HSU: Health service utilisation and outcomes population/ Heath contact population as a source of data/ denominator

Answer 6

MoHealth record and report information from publicly funded healthservices.

• Can compare different regions, but purpose is to provide evidence for subsidy.
• Can track outcomes of deidentified person

Question 7

What is Nationally Representative surveys : Eg. NZ health survey
as a source of data/ denominator

Answer 7

20,000 ppl/yr get asked.

• Don’t get a history of the people
• Can ask about attitudes to risk- however all answers will be self reported

Question 8

What are the key differences between HSU and Nationally representative surveys

Answer 8

• NRS: self reported data: may not be honest so bias.

- HSU: objective data: coded, general picture of health and wellbeing using international standards of statistics

Question 9

What is Ad Hoc surveys as a source of data/ denominator

Answer 9

Survey with no plan for repetition used by market research companies to gauge qualitative or quanitive
weakness: may not be generalisable to the wider population: who has been counted?

Question 10

What is the IDI as a data source

Answer 10

Routinely collected information from many government/ other agency sources.
All deidentified unit record (following individual/household) - All of NZ linked to form a population base.

Weakness compared to census: Activity data set: to be counted you have to interact with the system: police, tax, acc etc– the population might change

Question 11

What are the main considerations we have to take into when using Data from these sources

Answer 11

Is it ethical?
Purpose of collection vs use in analysis match?
Population vs population samples, representative of NZ?
Objective vs subjective measures of health/ other determinants.

Question 12

Whats the difference between population structure and population composition

Answer 12

Both are measures (% or counts) of attributes (variables) in a population.
Pop Structure: Age and Sex
Pop composition is all other attributes

Question 13

How do you read a population pyramid

Answer 13

x axis: male-> female

y axis: young->oldq

Question 14

What events determine population structure

Answer 14

Vital events:

• Change in fertility rates/infant mortality- dramatic but time lag
• Changes in adult mortality rates: less dramatic/variable over time as its spread over a wider age range
• Migration can have a dramatic effect especially if there is a age/sex specific trend

Question 15

How does population structure affect events?

Answer 15

Because fertility, mortality and migration are not evenly distributed across the population by age and sex. Some populations with an age group heavy structure can therefore influence the distribution of some of these fertility, death rates and migration events

Question 16

What are dependency ratios and what are the three categories you can calculate and how do you calculate total

Answer 16

The ratio of children and elderly to working age people- how many people are they supporting through their taxes? Can be calculated for both together for total or each factor separately.
Total: children+ elderly / working age people * 100

Question 17

How to calculate dependency ration of child: Neontic

Answer 17

Child: 0-14yrs/ working age person (15-64) * 100

Question 18

How to calculate dependency ration of elderly: Gerontic

This is expected to be higher than children by 2026

Answer 18

> 65yrold/ working age person (15-64) * 100

Question 19

What is the issue of dependency ratio

Answer 19

They don’t take into account who is in the working age population who is actually contributing to tax. And some elderly still contribute to tax.

Question 20

Compare the two population impacts of ageing: natural and absolute decline of a population

Answer 20

Natural decline of the population: occurs when there are more dying than being born in a population: - absolute+ structural aging

Whereas Absolute decline: occurs when there is insufficient migration to replace ‘lost’ births and increased deaths
- not in Nz but some europe/asia

Question 21

What is the demographic transition

Answer 21

4 stages showing the change in population demographics as a country progresses economically/socially.

Question 22

What is stage 1 of demographic transition: pre transition +pyramid

Answer 22

stage 1: prior to industrial revolution: High death & high birth rates give a triangle pyramid: more to support the elderly but fairly small constant population size

Question 23

What is stage 2 of demographic transition: health, sanitiation: least developed countries today

Answer 23

Declining mortality rates but same high birth rates lead to and slow increase of total population. Compounding of population growth makes a bottle shape pyramid

Question 24

What is stage 3 of demographic transition:

womens status/ contraception: developing countries today

Answer 24

Declining birth rates, even lower death rates leading to population growth not so fast anymore.
pyramid is a fingernail.

Question 25

What is stage 4 of demographic transition: NZ and other developed countries today

Answer 25

Low fertility and low mortality converge together to stabilise the population (now big but not growing). Equal proportion of child and elderly dependency ratio

Question 26

What is numerical vs structural ageing

Answer 26

Numerical is the actual number of elderly increasing - inevitable whereas
Structural is increase of the proportion of population that is elderly. - could be reduced fertility rates