Where issues have been assigned to policy subsystems, the venue change process can lead to dramatic reversals in policy outcomes. We use the term “subsystem collapse” to refer to changes in subsystem organization which enable interests not generally supportive of the involved industry to intrude in the policy process in critical ways. Other scholars have described changes in subsystem politics in different terms, and of course we recognize that there are degrees of collapse.
(Baumgartner and Jones, 1991: 1051)
Baumgartner, F and Jones, B. 1991. Agenda Dynamics and Policy Subsystems. Journal of Politics Vol. 53, (4). pp.1044-1074.