Policymakers transfer knowledge about policies, ideas, and institutions between political systems, learning from one another in a process of policy learning; lesson drawing; diffusion; or policy transfer. As Dolowitz and Marsh observe: “While terminology and focus often vary … studies are concerned with the process by which knowledge about policies, administrative arrangements, institutions, and ideas in one political system (past or present) are used in the development of policies, administrative arrangements, institutions and ideas in another political system.” The literature on policy transfer has mainly addressed how policymakers glean potential lessons and use those experiences to devise reforms. It asks questions about why policy transfer occurs; who was involved; what was transferred; from where; the extent of the transfer; and how the process of transfer is “related to policy ‘success’ or ‘failure.’” Greener distinguishes this from policy learning, where policymakers make deliberate adjustments in response to experience or new information, and learning is evident when policy changes as a result of this process. Some scholars see policy transfer as a subset of policy learning, since these are often part of the same procedure. Oliver and Pemberton advance a model, for example, of how ideas are absorbed through learning, in which bureaucratic battles ensue to institutionalize a new policy, and reformers' success in securing support can be critical in determining the extent of policy learning and transfer.