Why are policy agendas punctuated? Friction and cascading in parliament and mass media in Belgium

This study focuses on a central question in the literature on policy agendas and punctuated equilibrium: why are some agendas more punctuated than others, and what causes these punctuations? In particular, is it friction - wherein barriers to change lead to the build-up of tension that finally overflows - or rather cascades that occur owing to positive feedback loops as actors imitate other actors? We hypothesize that both are at work, and that under certain conditions - e.g., the number of actors and the amount of communication between them - one mechanism is stronger than the other. We test our hypotheses with data on parliamentary activities (interpellations and oral questions) and media coverage in Belgium in the 1990s. We find evidence of both friction and cascading contributing independently to the typical punctuated pattern of policy agendas.