This document critiques Nassim Nicholas Taleb's theory of "black swan events", which are unpredictable outliers that have disproportionate effects. The author argues that in disaster risk reduction, scenarios can combine past disasters with forecasts to anticipate many future impacts. While very rare events may be hard to predict precisely, their elements are not entirely novel and their consequences are not unpredictable. The "black swan" concept should not be accepted without questioning in disaster risk analysis.

1. WHY BLACK SWANS DO NOT EXIST
IN DISASTER RISK REDUCTION
a critique of Nassim Nicholas Taleb's theory
Prof. David Alexander

2. THE CONCEPT

3. Europeans believed that all swans were white
until they went to Australia and saw a black one.
It was a totally unpredicted discovery. No theory
or tendency pointed towards the existence of
swans of a different colour.

4. The black swan: an extreme outlier
Black swan theory - Nassim Nicholas Taleb
(b. 1960), Lebanese-American economist

5. "The central idea in The Black Swan
is that rare events cannot be
estimated from empirical
observation because they are rare."
- Nassim Nicholas Taleb

6. "We know from chaos theory that even if
you had a perfect model of the world, you
would need infinite precision in order to
predict future events. With sociopolitical or
economic phenomena, we do not have
anything like that."
- Nassim Nicholas Taleb

7. Concerning his intellectual abilities, Taleb has
been the subject of supercharged hype.
Closer analysis shows that his ideas have merit
but should not be accepted unquestioningly.

8. He is fond of aphorisms which, if they are
apposite, are distilled wisdom, and, if they are
not, are misleading oversimplifications.

9. In disaster risk
reduction, the use
of scenario
methods enables
us to combine
elements from
past disasters with
forecasts of future
developments.
Very few impacts
in the future will be
entirely
unanticipated.

10. Conventionally, we have used a Gaussian
('normal') distribution of magnitude versus
frequency: many small events have little effect
and so do few large events. The greatest problem
is with medium events, perhaps with a frequency
of once in ten years.

11. Falling
hazard
probability
Rising
vulnerability
Optimum
mitigation
level?
'Fat-tailed'
(negatively skewed)
distribution
Magnitude
Frequency
EXTREME EVENTS MAY BE MORE LIKELY THAN
PREDICTED UNDER A GAUSSIAN DISTRIBUTION

12. ECONOMICS

13. DISASTER
Destruction
damage casualties
CAPITAL LABOUR
(fast) reformation (slower) repopulation
temporary boom
in employment
Reconstruction
Recovery
capital displaces labour unemployment and
social consequences
Slump

14. Reckless
lending
Reckless
borrowing
DEBT DEMOCRACY
Austerity
Inequality
Marginalisation
Disaffection
Disaster
impacts
Growing
vulnerability

15. "The track record of economists in
predicting events is monstrously
bad. It is beyond simplification; it is
like medieval medicine."
- Nassim Nicholas Taleb

16. ANTIFRAGILITY

17. vere magnum habere in se fragilitatem
hominis ac securitatem Dei
It is a sign of true greatness to have the
fragility of a man together with the self-
confidence of a god.
Lucius Annaeus Seneca, 4BC - AD65

18. Fragility, from the Latin fragilitas, is the quality of
being easily broken. For the inanimate world, a
fragile material is one that is liable to be
damaged or destroyed. If it lacks an adequately
robust structure, it can be described as weak: if
by its very nature it lacks resistance to applied
forces, it can be termed delicate.

19. MATERIALS SCIENCE
• physics, chemistry
• engineering
ENVIRONMENTAL ISSUES
• climate change adaptation
• global change
• sustainability
• disaster risk reduction
PHILOSOPHY
• precariousness of
the human condition
ECONOMICS
• risk of financial collapse
POLITICAL SCIENCE
• fragile states
FRAGILITY
PSYCHOLOGY
• precarious self-image
macroscopic
microscopic
The concept of fragility has at least six dimensions

20. "When you ask people, 'What's the opposite
of fragile?,' they tend to say robust,
resilient, adaptable, solid, strong. That's not
it. The opposite of fragile is something that
gains from disorder."
- Nassim Nicholas Taleb
Antifragility - systems exhibit an ability to
benefit and grow from volatility.

21. "We humans, facing limits of knowledge,
and things we do not observe, the unseen
and the unknown, resolve the tension by
squeezing life and the world into crisp
commoditized ideas".
- Nassim Nicholas Taleb, The Bed of
Procrustes

22. CONCLUSION

23. Economics is an exceptionalist
discipline, one whose ideas cannot be
transferred easily to other disciplines,
even within the social sciences.

24. Self-condemnation?
"Being an economist is the least ethical profession,
closer to charlatanism than any science."
- Nassim Nicholas Taleb
"A good maxim allows you to have the last word
without even starting a conversation."
- Nassim Nicholas Taleb

25. "If you give advice, you need to be
exposed to losses from it."
Taleb, Commencement Address,
American University of Beirut, 2016

26. The problem is not Taleb and his
ideas, but their unquestioning
acceptance by people who would
rather follow them than think.

27. "Failure saves lives. In the airline industry, every time a
plane crashes the probability of the next crash is
lowered by that. The Titanic saved lives because we're
building bigger and bigger ships. So these people died,
but we have effectively improved the safety of the
system, and nothing failed in vain."
- Nassim Nicholas Taleb
In systemic terms, the wreck
of the Costa Concordia in
2012 was a rerun of the
wreck of the Titanic.

28. Rare, exceptionally large events are not
unpredictable, and neither are their
consequences. Each element of an
exceptional disaster has occurred before.
The combination is unique, but the
elements and their antecedents are not.

29. I fear that in disaster risk reduction the black
swan may be extinct and its ecological niche may
be occupied by the red herring.

30. DISASTER
POLITICS
ECONOMICS
SOCIAL CONDITIONS
PHYSICAL IMPACT
Politics in
the service
of economics
VULNERABILITY
knowledge is ideology
Complexity
Ideology
• extremism
• separatism
• isolationism
• exclusion
• austerity
Conflict
Climate change
Demographic change
• human mobility
Culture
Underlying risk drivers
[x]