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Evaluating Common FuturesRethinking Prescriptivism and Descriptivism
Kian Mintz-Woo
CCFC2015
UNESCO—July 10, 2015
2
• Cost Benefit Analyses addresses trade-offs
btw. present & future consumption
• This often involves determining the
contribution of consumption to utility η;
equivalently, curvature of utility function
• I introduce two worries for assigning a value to
this parameter stemming from behavioral
psychology
Evaluating Climate Policies
3
• In IPCC SAR WG3, Arrow et al. (1996) called
the methodologies descriptivism and
prescriptivism (cf. Manne 1995)
• Descriptivists think we should assign values to
normative parameters (e.g. η) by aggregating
actual revealed, or stated, preferences
(Nordhaus)
• Prescriptivists think ethical theorizing
unavoidable so it should be explicit (Broome,
Stern, Dasgupta)
Descriptivism/Prescriptivism
4
• Prospect theory tells us that
decisions elicited under risk will
be irrational in a predictable way
• Kahneman and Tversky (1979)
tells us that individuals judge
gains and losses asymmetrically, with (1)
different concavity and (2) non-differentiability
about the origin
Prospect Theory
5
Thus, prospect theory
generates “normatively
unacceptable consequences,
such as inconsistences,
intransitivites, and violations of dominance”
(Kahneman 1979, p. 277)
A Problem for Descriptivists
6
• So any decisions elicited under risk will
be non-evaluative
• But this is a problem; any
savings/investment behavior is under
risk!
A Problem for Descriptivists
7
• One might thus adopt expert judgment
• On this view, economists or philosophers
make social judgments about the value of
parameters like η
Prescriptivism
8
• Behavioral psychologists tell us that, for target
questions that require complex, abstract
thought, one may substitute heuristic
questions
Heuristic Questions
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“How happy are you with
your life these days?”
A Target Question
10
“What is my mood right
now?”
A Heuristic Question
11
“How much would you
contribute to save
endangered species?”
Another Target Question
12
“How much
emotion do I
feel when I
think of dying
dolphins?”
Another Heuristic Question
13
Choosing values of η fits all of these
criteria:
• it is difficult;
• there is an obvious emotionally valenced
heuristic (Finucane 2000);
• and there is no simple check
A Problem for Prescriptivism
14
• So the target question:
“What is the elasticity of
marginal utility of
consumption η?”
A Problem for Prescriptivism
15
…could be replaced by:
“How do I feel when I
imagine having different
levels of consumption?”
A Problem for Prescriptivism
16
• If we take these strains of psychology
seriously, they undermine judgments of η on
both the descriptivist and the prescriptivist
views
• They will give us distorted results from
prospect theory, or mere heuristics
• What should we do? I think we should hold
our value judgments for η a less securely
Conclusion
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