13.1 Historic Tolerance Thresholds
189
changed over time some passages below are strongly inspired from Improving Sustainability through Reasonable Risk and Crisis Management (https://www.riskope.
com/knowledge-centre/tool-box/books/) (Oboni and Oboni 2007).
The straight line in the log-log plot was called the boundary Line in early literature
(Farmer 1967; EDI 1989). As per the exponent b, a value smaller than −1 indicates
risk averseness whereas b larger than −1 indicates risk appetite (Plattner 2005).
Generally human beings have an appetite for voluntary risks, but an averseness to
involuntary risks. Moreover, many Perception Affecting Factors (PAF)
1 enter into the
delicate equilibrium between risk averseness and appetite, as described in Table 13.3.
Table 13.3 The delicate equilibrium between risk averseness and appetite
PAF
Represents
Voluntariness
Voluntariness
Reducibility
Reducibility, predictability, avoidability
Knowledge
Familiarity, knowledge about risk, manageability
Endangerment
Controllability, number of people affected, fatality
of consequences, distribution of victims
(spatio-temporal), scope of area affected,
immediacy of effects, directness of impact
Subjective measure of extent of damage
Extent of damage
Subjective measure of frequency of event
Frequency of event
1
10
100
1000
10000
1.0E-9
1.0E-8
1.0E-7
1.0E-6
1.0E-5
1.0E-4
1.0E-3
1.0E-2
1.0E-1
1.0E+0
Number of Fatality
Probability per Annum
EC 2006 Max
EC 2006 min
NSW 2011 Max
NSW 2011 Min
HK Max
HK Min
ANCOLD 2003
Whitman 1984 Max
Whitman 1984 Min
Fig. 13.1 Comparison between various risk tolerance thresholds, consequences expressed in fatalities. Notice that the vertical axis (probabilities per annum) extends well below the credibility
threshold for a number of examples
1 Whereas Plattner (2005) considers that perceived risks to be generally higher than real, objective
risks, we take the stance of possible overestimation and possible underestimation of risks, as factors
as familiarity, knowledge, controllability etc. blatantly lead people to underestimate risks they are
exposed to.
189
changed over time some passages below are strongly inspired from Improving Sustainability through Reasonable Risk and Crisis Management (https://www.riskope.
com/knowledge-centre/tool-box/books/) (Oboni and Oboni 2007).
The straight line in the log-log plot was called the boundary Line in early literature
(Farmer 1967; EDI 1989). As per the exponent b, a value smaller than −1 indicates
risk averseness whereas b larger than −1 indicates risk appetite (Plattner 2005).
Generally human beings have an appetite for voluntary risks, but an averseness to
involuntary risks. Moreover, many Perception Affecting Factors (PAF)
1 enter into the
delicate equilibrium between risk averseness and appetite, as described in Table 13.3.
Table 13.3 The delicate equilibrium between risk averseness and appetite
PAF
Represents
Voluntariness
Voluntariness
Reducibility
Reducibility, predictability, avoidability
Knowledge
Familiarity, knowledge about risk, manageability
Endangerment
Controllability, number of people affected, fatality
of consequences, distribution of victims
(spatio-temporal), scope of area affected,
immediacy of effects, directness of impact
Subjective measure of extent of damage
Extent of damage
Subjective measure of frequency of event
Frequency of event
1
10
100
1000
10000
1.0E-9
1.0E-8
1.0E-7
1.0E-6
1.0E-5
1.0E-4
1.0E-3
1.0E-2
1.0E-1
1.0E+0
Number of Fatality
Probability per Annum
EC 2006 Max
EC 2006 min
NSW 2011 Max
NSW 2011 Min
HK Max
HK Min
ANCOLD 2003
Whitman 1984 Max
Whitman 1984 Min
Fig. 13.1 Comparison between various risk tolerance thresholds, consequences expressed in fatalities. Notice that the vertical axis (probabilities per annum) extends well below the credibility
threshold for a number of examples
1 Whereas Plattner (2005) considers that perceived risks to be generally higher than real, objective
risks, we take the stance of possible overestimation and possible underestimation of risks, as factors
as familiarity, knowledge, controllability etc. blatantly lead people to underestimate risks they are
exposed to.