Economics, Rational Choice Theory and Utility Maximization

Economist Geoff Hodgson has a short article at Evonomics on the issue of the theoretical and methodological status of the rationality principle in economics. Hodgson sketches an argument that he has more fully developed in his book From Pleasure Machines to Moral Communities. In a nutshell, Hodgson argues that the rationality principle, according to which individuals act such as to maximize their utility, is (i) not a tautology but (ii) is unfalsifiable. Let me take these two points in order.

First, Hodgson argues that the rationality principle is not a tautology because utility maximization “is potentially false”. That is, there may be cases where people’s choices fail to maximize their utility. We may suppose that the non-maximizing behavior may be intentional or not: there are cases where we intend to maximize our utility but we fail, for instance because of weakness of will (a phenomenon known as Akrasia in ancient Greece); there are other cases where reason provides us with good reason to make choices that do not maximize our utility. This latter possibility is at the core of Amartya Sen’s criticism of rational choice theory developed in the 1970’s. Second, Hodgon points out that in spite of the fact that the U-max assumption may be false, we can never know when or at least we can never establish that is false in any specific case. This is due to the fact that it is at least always possible to change the description of some decision problem such as to make the observed behavior compatible with any consistency assumption and thus utility maximization. This is indeed true in all versions of rational choice theory, either under the form of revealed preference theory or of expected utility theory. The basic strategy consists in changing the description of the outcome space of the decision problem such as to make the choice behavior consistent. Unless a behavior is completely random, there should always be in principle a way to rationalize it according to some consistency criterion. U-max only requires transitivity of the underlying preference ordering (plus some reflexivity and continuity conditions). According to Hodgson, these two points make rational choice theory useless as a theory of human behavior. In particular, he rightly note that rational choice theory applies equally well to machines, insects and animals and that as a consequence it cannot tell us anything specific about humans.

I partially agree with Hodgson but his argument requires some qualifications. More specifically, I would argue that (i) actually rational choice theory is a tautology and that (ii) the fact that is unfalsifiable is not necessarily problematic depending on its purpose. Consider the former point first. The only reason Hodgson can validly claim that utility maximization is not a tautology is because he takes utility to be something to be independently measurable. This is of course the way the utility concept was understood by Bentham and by the first marginalists. There is also a bunch of behavioral economists defending a “back to Bentham” paradigmatic move who speak in terms of “experienced utility”, where the latter refers to something akin to happiness or pleasure. Finally, we may also admit that some economists of the Chicago school may have entertained an interpretation of utility as something independently measurable. But all of this is unorthodox. Since the days of Pareto and Samuelson, economic theory (and especially consumer theory) has given up the interpretation of utility as an independently measurable quantity. The ordinalist revolution and Samuelson’s pioneering contribution to revealed preference theory have shown how consumer theory can be formulated without any reference to the utility concept. More exactly, they have established that utility maximization is nothing but a mathematically convenient statement equivalent to the assumption that people make consistent choices and/or have well-ordered preferences. The same is true for expected utility theory, especially Savage’s version which is explicitly behaviorist. Absolutely nothing is assumed regarding what happens “in the head” of the person making some choice. U-max is not an assumption; it is only a descriptive statement of what one is doing. It is a tautology as long as there is always a possibility to rationalize one’s choices in terms of some consistency condition.

Consider now the second point. The fact that the U-max principle is actually a tautology only strengthens Hodgson’s claim that it is unfalsifiable. You cannot falsify a tautology as it is true by definition. Does it make it useless from a scientific perspective? The short answer is clearly “no”. Science is full of useful tautologies, also in economics. Consider only one example coming from biology, one on which Hodgson extensively relies in his work: the Price equation. The Price equation is a highly general mathematical statement of a process of differential replication, i.e. natural selection. The mathematical beauty of the Price equation is that whatever the specificities of the actual process of selection (whether organisms are haploid, haplodiploid, diploid, whether it is cultural or genetic, …), it captures them in a straightforward formula according to which, to simplify matters, the growth rate of some trait in a population can be expressed as the covariance between the trait frequency and the fitness of its bearer. Under the classical meaning of fitness (a measure of reproductive success), Price equation is of course both unfalsifiable and a tautology. But no biologists or behavioral scientists would reject it for this reason. The usefulness of the Price equation comes from its value as a problem-solving device. It gives the scientist a methodological strategy to solve empirical or theoretical problems. As an instance of the latter case, consider for instance how Price equation is useful to derive Hamilton’s rule and to make explicit the assumptions on which the latter rely regarding the property of selection and inclusive fitness.

I would argue that the same is true for rational choice theory in economics. From a Weberian point of view, rational choice theory provides us with a methodological strategy to uncover people’s motivations and reasons for action. Similarly, Don Ross argues it is part of the “intentional stance strategy” through which we are able to understand and predict agents’ behavior. Hodgson is right that rational choice theory is rather weak as an explanatory theory of individual behavior, simply because the theory suffers from an obvious problem of under-determination. But individual behavior is not the right level at which the theory should be applied. It is way more useful for instance to understand how the change in the institutional framework, by modifying people’s incentives and beliefs, may affect their behavior. This strategy is at the core of the applied branch of microeconomics, known as mechanism design. A branch which has enjoyed some empirical successes recently. Of course, there are other reasons to reject the imperialistic claims of the proponents of rational choice theory. I explore some of them in this (version of a) forthcoming paper in the Journal of Economic Methodology.