[영문]This historical-institutionalist case study of public-private change in the rehabilitation health sector in Ontario, Canada, seeks to build on literature about the politics of policy drift, particularly with respect to health care systems. Rather than turning to higher-order institutional factors, such as federalism and overall financing agreements between states and the medical profession, or to economic indicators such as change in expenditures, however, it posits that the particularities of how welfare-policy sectors are organized with respect to their decision-making contribute to drift. Such organization is framed by two factors. The first is the set of rules by which the public-private boundary is drawn, and the second is the structuring of public institutions that set legislation and regulation, and organize the policy networks attendant on them, around these boundaries. The degree of coordination or fragmentation among these, this case suggests, is a factor in the politics and dynamics of drift.