Measuring the stasis: Punctuated equilibrium theory and partisan polarization

Abstract The American policy process is characterized by a pattern known as “Punctuated Equilibrium,” manifesting as periods of stasis interspersed with large periods of change. Punctuated equilibrium suggests that friction in the policy process and uneven information processing result in a policy process that over‐ and underreacts to problems. Increasingly, American political institutions are also characterized by high levels of partisanship, which are rising steadily and represent one of many sources of institutional friction. We argue that with increased polarization, the policy process has become longer, exaggerating patterns of stasis and punctuation—the periods of stasis being more prolonged and punctuations less frequent. In sum, increased partisan polarization in Congress amplifies patterns of punctuated equilibrium. We test this theory using data from the Comparative Agendas Project on the federal budget and public laws, using kurtosis scores to measure the relative force of punctuations versus statis. We find increasingly leptokurtic distributions of budget changes from 1948 to 2020, but a decreasingly leptokurtic distribution of public law passage across the same time. These findings indicate that polarization has resulted in exaggerated patterns of punctuated equilibrium in the legislative process, and a tendency toward fewer, higher‐stakes public laws.