THE PURSUIT OF UNDERSTANDING:MODELLING DYNAMIC BEHAVIOUR IN

DISEASE, LIFE & LOVE

Brian DangerfieldProfessor of Systems Modelling

Centre for OR & Applied Statistics

System Dynamics modelling is based upon: * Concept of Information Feedback

* Delays

* Mapping Tools– Stock-Flow Diagrams– Influence Diagrams

* Equations linking variables to one another in the system

Chou En-lai (1898-1976)

- asked for his assessment of the effects of the French Revolution

•At what minute did most people enter the bar?

•At what minute did most people leave the bar?

•At what minute were most people in the bar?

•At what minute were fewest people in the bar?

A stock-flow diagram

In the barEntering Leaving

COCAINE PREVALENCE IN THE USA

Survey data suggested lifetime prevalence estimates were falling rapidly in the latter part of 1980’s.

Argument for more resources to support policies of interdiction & incarceration (rather than prevention).

But reported decline physically impossible (Homer);

-Survey collected biased data

Current &Past Users(lifetime

prevalence)

first timecocaine use

death fromall causes

Limits on Our Capacity for Processing Information

7 + 2

George Miller, Psychological Review63:2 (1956) pp. 81-97

5 variables A, B, C, D, and E

A= f (B,C,D)

B= f (C, E)

C= f (B,A)

D= f (C, E)

E= f (B,C)

A

B C

E

D

Who are the most important people involved in securing

the safe passage of an aircraft from A to B?

DYNAMICS OF AN EPIDEMIC

MILESTONES IN THE EVOLUTION OF THE HIV/AIDS MODEL

Number of Year (quarter) of

Feature equations (approx) introduction

Project-based model 13 1987(2)

Variable infectivity 20 1989(1)

Heterogeneity & changing behaviour 47 1990(2)

Reporting delay & fitting model to data 70 1992(2)

Treatment effect & removals / additions 120 1997(4)

Health care sector 190 1998(4)

Introduction of HAART 300 1999(2)

Effects of regression in behaviour

after HAART (fitting to HIV data) 360 2001(3)

Estimated Numbers & Percent on HAART at end-1998

Homo/bisexual men only

Estimated Number Percent of total

of Patients

U.K. 10734 67%

France 17500 64%

Germany 10359 69%

Netherlands 2069 76%

FASHION ITEM DYNAMICS

TOURIST DEVELOPMENT IN ISLAND ECONOMIES

Need a balance between economic gain and environmental conservation.

For: jobs; tax revenue; foreign currency earnings

Against: environmental pollution; higher cost of living; migration from agriculture to tourist services

SUSTAINABLE DEVELOPMENT IN AN ISLAND TOURIST ECONOMY

Environmental deterioration might affect the numbers and/or mix of tourist visitors— no rail links - congested motorways— Reina Sofia airport congestion— obsolete tourist facilities; poor professional training

Issues:— water supply— waste collection and treatment— communications— health care— noise pollution— public safety

DIFFUSION OF AN INNOVATION

Barriers to innovation:

–QWERTY Keyboard : Sholes vs Dvorak

–VHS video format vs Betamax

Sharp take-off innovations:

–CAT scanners

–Mobile phones

“CLUBBED TO DEATH” (Student Direct Dec. 2002)

• Superclubs are suffering … Renaissance; Gatecrasher, Cream.

• How did things go so wrong?– Competition – more clubs and (now) bars.– Merchandising (In 2000, 5% of MoS

profits came from the clubs).– Big name DJ’s charged at least £10K per

set.– Higher door prices.

visiting rateper club

spin-offmerchandising

(brand awareness)

average clubdoor price

new clubopenings DJ fees

new baropenings

numbers in clubper week

profits

-

+

+

-

++

+

+

- -

+ +

+1

2

34

5

6

+

SARAWAK (EAST MALAYSIA)

• CORAS/CER Two year research project

• Economic model for the State Government

Model Purpose?

Map of Borneo

Sarawak Gross Domestic Product 1980 – 1999

(Constant Prices)

02,0004,0006,0008,000

10,00012,00014,000

1980 1983 1986 1989 1992 1995 1998

Years

GD

P R

M M

illio

ns

DYNAMIC HYPOTHESIS: DYNAMIC HYPOTHESIS: high-level maphigh-level map

Primary & SecondaryEducation

HigherEducation

(Arts)

HigherEducation(Science)

VocationalEducation

(Sub-professional)

R & D Centres

(Exemplars)

Primary Industry

(Agric; Forestry;Mining; M/facturing)

Knowledge-basedIndustry & Services

High Value-added; Biotech; Medicine

SecondaryIndustry

(Transport; Storage;Retail; Finance &

Insurance)

BroadbandCabling (Kms)

Number of PC’s

State Incentives

FederalFunds

ICT Infrastructure

StateRevenue

SUPPLY

DEMAND

COMMSINFRASTRUCTUREF

DI

Closures?

Leakage

Overseas?

Skills/Tech Transfer Money

Capital Equipment Human Resources

Virtuous circles (positive loops): if ICT Resources (actual)>= ICT Resources (desired). Otherwise negative

loops come into play & positive loops shifted from growth to decay mode

K.Industries

ICT Resources(desired)

ICT Resources(actual)

Supply ofHigh-Tech Human

Capital

R&DCentres

+

+

++

+

-

-

+

++

+

DYNAMICS OF A PARTNERSHIP

Sustainable Futures:

Endgames:

Sustainable Futures:

‘Golden Wedding’

0

Time

+

-

Sustainable Futures:

‘Amo et Odi ’

0

+

-

Time

Endgames:

‘We’re still good friends’

0

+

-

Time

Endgames:

‘Mutual loathing’

0

+

-

Time

EU Divorce Rates in 2001 (per '000 population)

EU Divorce Rates in 2001 (per '000 population)

2.6 2.72

2.6 2.9

0.9 1 0.7 0.7

1.9

00.5

11.5

22.5

33.5

UK Marriages

406000

286000

0

100000

200000

300000

400000

500000

1976 2001

England & Wales Divorce Rates per '000 Married Population

0.00

5.00

10.00

15.00

1976 1981 1986 1991 1996 2001

England & Wales Re-marriages of one or other partner (% of all marriages)

6

16

2327

0

5

10

15

20

25

30

1964 1974 1984 1994

Median duration of marriage at divorce (yr)

11.511.3

10.19.8

8.59

9.510

10.511

11.512

1963 1973 1983 1993

Co-habitation (%) of single non-married women

8

31

05

1015

20253035

1979 1998

• The UK picture??

• Fewer Sustainable Futures & more Endgames ??