A three-state dynamical model for religious affiliation

•Presents a generalised class of the ‘three state’ model of social groups.•A range of these models are examined in relation to data for religious commitment in post WWII Northern Ireland.•These models suggest that there have been negligible religious conversion/reconversion rates with in Northern Ireland over the last 70 years.

In the last century the western world has seen a rapid increase in the number of people describing themselves as affiliated with no religious group. We construct a set of models using coupled differential equations in which members of a society can be in one of three groups; religiously committed, religiously affiliated or religiously not affiliated. These models are then used to analyse post World War II census data for Northern Ireland.