The rational actor and its critics: economics beyond the model
The rational actor and its critics: economics beyond the model
Almost everything in A-level Economics rests on the assumption that people are rational maximisers. It is a powerful simplification and a contested one, and understanding both the power and the contest is what marks out strong Economics and PPE applicants.
Open an A-level Economics textbook and you meet, on the first page and every page after it, a particular kind of person. This person has stable preferences, aims to maximise their own utility or profit, and reasons with full information towards the best available choice. The consumer, the firm and the worker all behave this way. Most of the results you learn, and the diagrams we discuss in our piece on using diagrams to earn marks, follow from this assumption. It is worth understanding why economists make it, and why many of them spend their careers arguing with it.
Why the assumption earns its place
The rational, self-interested agent is not a claim that people are actually like this. It is a modelling device, and its defence is pragmatic. Milton Friedman made the case in 1953: a model should be judged by the accuracy of its predictions, not by the realism of its assumptions. A model of the firm that assumes profit maximisation may predict how firms respond to a tax rather well, even though no manager sits down to solve the equations. The assumption is useful because it is tractable. It yields determinate answers, and those answers are often close enough to be worth having. The simplicity is a feature, not an embarrassment.
Where it strains
The trouble is that the deviations from the model are neither random nor small. From the 1950s Herbert Simon argued that real decision-makers do not maximise but satisfice: they lack the information and the computing power the model assumes, and they settle for an outcome that is good enough. From the 1970s the psychologists Daniel Kahneman and Amos Tversky showed that people depart from the rational model in systematic, predictable ways. We feel a loss more heavily than an equivalent gain. We are swayed by how a choice is framed. We anchor on numbers that ought to be irrelevant. Richard Thaler built these findings into economics itself, and the field of behavioural economics is the result. A separate line of attack came from information: George Akerlof showed that when buyers and sellers know different things, a market can unravel in ways the standard model never sees, and much of modern economics is about the consequences of information being costly and unequally held.
Assumptions are where the argument is
The deeper lesson is not that the textbook is wrong. It is that assumptions are not incidental scaffolding to be forgotten once the diagram is drawn. They are where the intellectual action is. Every result you learn rests on assumptions you can name, and naming them tells you exactly where and why the result will fail. A model of a perfectly competitive market assumes many buyers and sellers, free entry, and good information, and knowing that is knowing in advance which real markets it will describe well and which it will mislead you about. The economist Dani Rodrik puts it neatly when he describes economics not as a single model but as a library of models, the real skill being to choose the right one for the situation in front of you.
Not a demolition
It would be a mistake to take all of this as a refutation of the rational model, and it is a common one among students who discover behavioural economics and decide the old theory is finished. It is not. The rational agent remains the baseline against which the deviations are measured and understood. Behavioural economics is interesting precisely because it maps departures from a benchmark, and without the benchmark there is nothing to depart from. The mature position holds both in view at once: a powerful idealisation, and a growing account of where and why real people diverge from it.
For applicants to Economics or PPE, this is exactly the terrain an interview explores. Tutors rarely ask you to recite a model. They ask you to reason about its assumptions, and to say where it would break. Kahneman's own account of his research, and Thaler's history of behavioural economics, are among the books on our reading lists that open this out, and learning to argue with a model rather than only apply it is central to our admissions and subject tutoring.
