Events are a basic element in most dynamic microsimulation models. Events are what people do: birth, death, moving etc. According to the Event-Pump Architecture, the core driver of the model is a loop called the event pump. This loop controls when and where things happen in the model. The feature is inspired by the message pump, which is a central element in how Windows is programmed (Petzold, 1998). The method is used in the microsimulation model SMILE-DK (Stephensen, 2013) , in the official Danish population forecast (Hansen & Stephensen, 2014) and in a forthcoming agent-based analysis of the Danish housing marked.