Take-up of union membership depends upon the opportunity and propensity to join. The union default would automatically enrol workers as members but would subsequently allow them to opt out. It has been advocated as a policy to facilitate the opportunity to join. However, such efforts at increasing the opportunity to join are unlikely to work if workers have little propensity to join because they prefer self-representation or collective forms of non-union employee representation (NER). We examine whether preferences for self-representation and NER are significant factors in explaining the propensity for non-union workers in unionised workplaces in New Zealand to not join a union where there is already an opportunity to do so. We also examine whether this propensity to unionise is positively shaped by the influence of a proposed union default and whether the decision to stay in or opt out under a default is influenced by preferences for self-representation or NER.