Papers of Kota Saito
Published/ Forthcoming Papers

The PerceptionAdjusted Luce model
2018
Mathematical Social Sciences
93(1):
67–76
[pdf]

We develop an axiomatic model that builds on Luce's (1959) model to incorporate a role for perception. We identify agents perception priorities
from their violations of Luce's axiom of independence from irrelevant
alternatives. Using such perception priorities, we adjust choice
probabilities to account for the effects of perception. Our
axiomatization requires that the agents' adjusted random choice conforms
to Luce's model. Our model can explain the attraction, compromise, and
similarity effects, which are welldocumented behavioral phenomena in
individual choice.

On path independent stochastic choice (Previous Title: Average Choice),
2017
Theoretical Econoics
13(1):
61–85
joint with David Ahn (UC Berkeley) and Federico Echenique. [pdf]

We investigate stochastic choice when only the
average and not the entire distribution of choices is observable,
focusing attention
to the popular Luce model. Choice is path independent if it is
recursive, in the sense
that choosing from a menu can be broken up into choosing from smaller
submenus. While an important property, path independence is known to be
incompatible with continuous choice. The
main result of our paper is that a natural modification of path
independence, that we call {\em partial path independence}, is not only
compatible with continuity but ends up characterizing the ubiquitous
Luce (or Logit) rule.

Response Time and Utility,
2017
Journal of Economic Behavior and Organization
139(15):
49–59
joint with Federico Echenique.
[pdf]

Response time is the time an agent needs to make a decision. One
fundamental finding in psychology and neuroscience is that, in a binary
choice, the response time is shorter as the difference between the
utilities of the two options becomes larger. We consider
situations in which utilities are not observed, but rather inferred
from revealed preferences: meaning they are inferred from subjects'
choices. Given data on subjects' choices, and the time to make those
choices, we give conditions on the data that characterize the property
that response time is decreasing in utility differences.

Testing theories of financial decision making (Previous title: Testable Implications of Translation
Invariance and Homotheticity: Variational, Maximin, CARA AND CRRA Preferences),
2016
Proceedings of the National Academy of Sciences
113(15):
4003–370
[pdf] [submitted version] [online appendix (Proof of Theorem 4)]
joint with Federico Echenique and Chris Chambers (UC San Diego).

We provide revealed preference axioms that charac
terize models of translation invariant preferences. In particular, we
characterize the models of variational, maxmin, CARA and CRRA
utilities. In each case we present a revealed preference axiom that
is satised by a dataset if and only if the dataset is consistent
from the corresponding utility representation. Our results comple
ment traditional exercises in decision theory that take preferences
as primitive.

Impure Altruism and Impure Selfishness,
2015
Journal of Economic Theory
158:
336–370.[pdf]

Altruism refers to a willingness to benefit others, even at one's own expense. In contrast, selfishness
refers to prioritizing one's own interests with no consideration for
others. However, even if an agent is selfish, he might nevertheless act
as if he were altruistic out of selfish concerns triggered when his
action is observed; that is, he might seek to feel pride in acting altruistically and to avoid the shame of acting selfishly. We call such behavior impurely altruistic . Alternatively, even if an agent is altruistic, he might nevertheless give in to the temptation to act selfishly. We call such behavior impurely selfish .
This paper axiomatizes a model that distinguishes altruism from impure
altruism and selfishness from impure selfishness. In the model, unique
real numbers separately capture altruism and the other forces of pride,
shame, and the temptation to act selfishly. We show that the model can
describe recent experiments on dictator games with an exit option. In
addition, we describe an empirical puzzle that government spending only
partially crowds out consumers' donations, contrary to the prediction
based on standard consumer theory.

Savage in the Market,
2015
Econometrica
83:
1457–1495.
[pdf] [online appendix]
joint with Federico Echenique

We develop a behavioral axiomatic characterization of Subjective
Expected Utility (SEU) under risk aversion. Given is an individual
agent's behavior in the market: assume a finite collection of asset
purchases with corresponding prices. We show that such behavior
satisfies a ``revealed preference axiom'' if and only if
there exists a SEU model (a subjective probability over states and a
concave utility function over money) that accounts for the given asset
purchases.

Preferences for Flexibility and Randomization under Uncertainty,
2015.
American Economic Review
105:
1246–1271.
[pdf] [online appendix]

An uncertaintyaverse agent prefers betting on an event whose
probability is known, to betting on an event whose probability is
unknown. Such an agent may randomize his choices to eliminate the
effects of uncertainty. For what sort of preferences does a
randomization eliminate the effects of uncertainty? To answer this
question, we investigate an agent's preferences over sets of acts. We
axiomatize a utility function, through which we can identify the agent's
subjective belief that a randomization eliminates the effects of
uncertainty.

Social Preferences under Risk: Equality of Opportunity vs. Equality of Outcome, 2013.
American Economic Review 103: 3084–3101.
[pdf]

This paper introduces a model of inequality aversion that captures a
preference for equality of exante expected payoff relative to a
preference for equality of expost payoff by a single parameter. On
deterministic allocations, the model reduces to the model of Fehr and
Schmidt (1999). The model provides a unified explanation for recent
experiments on probabilistic dictator games and dictator games under
veil of ignorance. Moreover, the model can describe experiments on a
preference for efficiency, which seem inconsistent with inequality
aversion. We also apply the model to the optimal tournament. Finally, we
provide a behavioral foundation of the model.

Strotz Meets Allais: Diminishing Impatience
and the Certainty Effect: Comment, 2011.
American Economic Review 101: 2271–2275.
[pdf]

Halevy (2008) states the equivalence between diminishing impatience
(i.e., quasihyperbolic discounting) and the common ratio effect. The
present paper shows that one way of the equivalence is false and shows
the correct and general relationships: diminishing impatience is
equivalent to the certainty effect and that strong diminishing
impatience (i.e., hyperbolic discounting) is equivalent to the common
ratio effect.
Working Papers

Axiomatizations of the Mixed Logit Model
First Draft: July 29, 2017, Current Version: June 17, 2018. [pdf]

A mixed logit function, also known as a randomcoefficient logit function, is an integral of logit functions. Necessary and sufficient conditions are provided under which a random choice function can be represented as a mixed logit function. The axioms are based on the social surplus function proposed by McFadden (1978, 1981).

Approximate Expected Utility Rationalization
Current Version: June 17, 2018 joint with Federico Echenique and Taisuke Imai. [pdf][online appendix]

We propose a new measure of deviations from expected utility, given
data on economic choices under risk and uncertainty. In a revealed preference
setup, and given a positive number e, we provide a characterization
of the datasets whose deviation (in beliefs, utility, or perceived
prices) is within e of expected utility theory. The number e can
then be used as a distance to the theory.
We apply our methodology to three recent largescale experiments. Many
subjects in those experiments are consistent with utility
maximization, but not expected utility maximization. The correlation
of our measure with demographics is also interesting, and provides new
and intuitive findings on expected utility.

General Luce Model
First Draft: June 17, 2015, Current Version: July 3, 2017, joint with Federico Echenique. [pdf]

We extend the Luce model of discrete choice theory to
satisfactorily handle zeroprobability choices. The Luce model (or
the Logit model) is the most widely applied and used model in
stochastic choice, but it struggles to explain choices that are not
made. The Luce model requires that if an alternative $y$ is never
chosen when $x$ is available, then there is no set of alternatives from
which $y$ is chosen with positive probability: $y$ cannot be chosen,
even from sets of alternatives that exclude $x$. We relax this
assumption. In our model, if an alternative $y$ is never chosen when $x$
is available, then we infer that $y$ is dominated by $x$.
While dominated by $x$, $y$ may still be chosen with positive
probabilityeven with high probabilitywhen grouped with a comparable set of alternatives.

Random Intertemporal Choice
Current Version: Feb 24, 2016, joint with Jay Lu (UCLA). [pdf]

We provide a theory of random intertemporal choice. Choice is random due
to unobserved heterogeneity in discounting from the perspective of a
modeler. First, we show that the modeler can identify the distribution
of discount rates uniquely from random choice. We then provide axiomatic
characterizations of random discounting utility models, including
exponential and quasihyperbolic discounting as special cases. Finally,
we test our axioms using recent experimental data. We find that random
exponential discounting is not rejected and the distribution of discount
rates is statistically indistinguishable across treatments.

A Relationship between Risk and Time
First Draft: February 10, 2011, Current Version: April 23, 2015.
[pdf]

This paper investigates a general relationship between risk and time
preferences. I consider a decision maker who chooses between
consumption of a particular prize in one period and a different prize in
another period. The individual believes that today's good is certain,
and that, as the promised date for a future good becomes increasingly
distant, the probability of his consuming the good decreases. Under
these assumptions, this paper shows that the individuals exhibits the
common ratio effect, the certainty effect, and the expected utility if
and only if he discounts hyperbolically, quasihyperbolically and
exponentially, respectively.

Testable Implications of Models of Intertemporal Choice:
Exponential Discounting and Its Generalizations
First Draft: Nov 8, 2013 with the title ``Testable
Implication of Exponential Discounting '', Current Version: April 12,
2015, joint with Federico Echenique and Taisuke Imai. Submitted
[pdf]

We present the first revealedpreference characterizations of the most
common models of intertemporal choice: the model of exponentially
discounted concave utility, and some of its generalizations. Ours is the
first axiomatization of these models taking consumption data as
primitives. Our characterizations provide nonparametric
revealedpreference tests. We apply our test to data from a recent
experiment, and find that our axiomatization delivers new insights and
perspectives on a dataset that had been analyzed by traditional
parametric methods.
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