People and enterprises that are subject to the law find it useful to know what the law is at present, but then also to anticipate future rules. If laws are stable this is easily done. Stability is more common where the judicial branch is concerned, because precedents are often valued, and for good reason. They are more often followed by judges than by those involved in other methods of lawmaking. But in all of lawmaking, and even in the private sphere, there is value to consistency and certainty. And yet, surprises can be attractive if they are not confronted on a regular basis. In extreme cases, expectations can be usefully upended, as is intentionally the case with much retroactive lawmaking. As times change, and new circumstances and information become known, there is often reason for law, and certainly for private decisions and apparent preferences, to change and presumably to improve. This Chapter considers the optimal level of certainty over time. One conclusion is trivial: people would prefer a world in which law changes only when the value of change is greater than the value of certainty. Efficiency and utility are features of an endgame, and these goals are more important than is the process of decision-making, where predictability is often a means to the end, and simply a short-term instruction. At the other end of the spectrum from predictability, or reversals in the case of new information, is the possibility of introducing a random element in law, so that neither the lawmaker, the governed parties, not interest groups eager to get friendly laws enacted, know what to expect. Randomization is rare and would often suggest that lawmakers have no idea what they are doing. At the same time, both certainty and change can be costly in many ways. If predictability is treated as a goal or as a firm rule, new information and circumstances are ignored. And yet, a subtle objection to mistaking the goal of utility with the process of achieving it, or background rule of certainty, is that if people know that a rule will change, there is nearly inevitable discrimination between parties who entered a system of lawmaking at different times. This discrimination is normally objectionable on both moral and public-choice grounds. The tradeoff between predictability and a willingness to change, or simply to surprise people, is complicated, but some examination of this tradeoff in different settings is illuminating. This Chapter begins with the tradeoff between predictability and change over time. It then turns to the connection between change and uneven treatment, and competition among organizations that can serve and exploit this inequality, or simply different preferences.
Saul Levmore, "Predictability and Adaptation in Law and other Markets (chapter in a coming book: Research Handbook on Law and Time)", Coase-Sandor Working Paper Series in Law and Economics, No. 997 (2024).