We analyse the determinants of union membership in the UK using data from the BHPS (1991-2003).
Employing three alternative methodologies to control for the problem of initial conditions we find that union
membership remains persistent even after controlling for the unobserved effect. There is evidence of a
considerable correlation between the unobserved individual heterogeneity and the initial membership
status. Ignoring this overstates the degree of state dependence of union membership greatly. The extent
of state dependence in union membership status is notably higher in the (1991-1996) period estimates and
appears to be more pronounced in the case of male employees for the entire period under analysis. The
second period estimates reveal that unobserved heterogeneity has a more prominent impact in
determining future unionisation probability versus past union membership. Finally, the estimates suggest
that an individual´s propensity to unionise is determined by a mixture of industrial and personal
characteristics. This is at odds with earlier studies, such as Booth (1986) and Wright (1995), failing to
control for unobservable effects and concluding that personal attributes do not have a significant impact on
unionisation propensity