“Driving using the rear view mirror”The Dark Art of Population Forecasting

Catherine ScottRoss MaconachiePublic Health Research UnitWest Sussex County CouncilApril 2013

Some simple questions..

• How many people with diabetes will live in West Sussex in 2020?

• If we reduce obesity prevalence by 10% what impact will that have on future need for healthcare?

• What skills will people need in the future?

• What will the composition of households be in future?

• What types of housing will we need in the future?

• What migration will there be in and out of West Sussex in future?

‘The first Baby Boomer has come to collect Social Security, how cute….’

‘As you can see, by late next month you’ll have over four dozen husbands. Better get a bulk rate on wedding cake.’

50

55

60

65

70

75

80

1966 1976 1986 1996 2006 2016 2026 2036 2046 2056

Year

Milli

ons

Actual 1971-based 1977-based 1989-based

1998-based 2004-based 2006-based

Past population projectionsSource: ONS

Now let’s look at some (incorrect as based on rates derived from previous MYEs) projections!

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 20210

20000

40000

60000

80000

100000

120000

140000

160000

180000

Population by District 2011-2021

AdurArunChichesterCrawleyHorshamMid SussexWorthing

0-4

5-9

10-14

15-19

20-24

25-29

30-34

35-39

40-44

45-49

50-54

55-59

60-64

65-69

70-74

75-79

80-84

85-89

90+

6.0% 4.0% 2.0% 0.0% 2.0% 4.0% 6.0%

Males MYE 2011 Females 2011 Females SNPP 2021

Males 2021

WSx Population 2011 - 2021

4 key areas are:-

1. 50% more people aged 90+

2. Huge expansion in number people aged 65+

3. Growth in upper working age - consider 2031!

4. Contraction of key carer groups to support

This corresponds to an 25% increase in 65+, a 31% increase in 85+ and an old age dependency ratio increase of 19%

MIGRATION

Sensitivity analysis - the effect of fertility, mortality and aggregate migration

Cautionary tale 1

‘It will be years - not in my time - before a woman will become Prime Minister’

Margaret Thatcher, future Prime Minister, October 26th, 1969.

Cautionary tale 2

‘Earlier on today, apparently, a woman rang the BBC and said she heard there was a hurricane on the way... well, if you're watching, don't worry, there isn't!’

Michael Fish, weather forecaster, a few hours before the worst storm since 1703 hit South East England in October 1987

Weather forecast for Crawley last week on Met Office website

There is a 20% chance of precipitation on Thursday

Chart 5.1 GDP projection based on market interest rate expectations

The fan chart depicts the probability of various outcomes for GDP growth. To the left of the first vertical dashed line, the distribution reflects the likelihood of revisions to the data over the past; to the right, it reflects uncertainty over the evolution of GDP growth in the future. If economic circumstances identical to today’s were to prevail on 100 occasions, the MPC’s best collective judgement is that the mature estimate of GDP would lie within the darkest central band on only 10 of those occasions. The fan chart is constructed so that outturns are also expected to lie within each pair of the lighter green areas on ten occasions. Consequently, GDP growth is expected to lie somewhere within the entire fan on 90 out of 100 occasions. The bands widen as the time horizon is extended, indicating the increasing uncertainty about outcomes. See the box on page 39 for a fuller description of the fan chart and what it represents. The second dashed line is drawn at the two-year point of the projection.

The effective of housing assumptions – various scenarios

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

2024

2025

2026

2027

2028

2029

2030

2031

750000

800000

850000

900000

950000

1000000

Population of West Sussex - Various Scenarios to 2030

ONS +5%ONS

Housing YoungFam

Housing Oldfam

WSCC Model

Natural Change

Natural Change -5%

Cautionary tale 3

‘They couldn't hit an elephant at this dist- ‘ Last words of Gen. John Sedgwick, spoken as he looked out over the parapet at enemy lines during the Battle of Spotsylvania in 1864.

Cautionary tale 4

‘There is not the slightest indication that nuclear energy will ever be obtainable. It would mean that the atom would have to be shattered at will’

Albert Einstein, 1932

Key messages

• Vital to have best population data possible

• Implications of different structures need to be understood by policy makers

• Dependency ratio an important statistic in the south east

• Key drivers of migration are jobs and housing, both can be influenced