Abstract
English adult social care commissioners are expected to make ‘evidence based’ decisions on how best to invest public sector funding. This study explores the types of evidence that commissioners use in relation to prevention services for older people and the other factors that influence their investment decisions. A study of local authority Directors of Adult Social Services (DASSs) was used to identify three local prevention interventions. Semi-structured interviews with leads for these interventions explored the evidence and other factors that influenced the investment process. Commissioners drew on a variety of published evidence, in particular that deriving from central government and its regional representative bodies, and third sector organizations with specialist knowledge. Local evidence was also generated through the undertaking of pilots and gathering of performance data. Alongside these ‘rational’ decision-making processes were strong political, personal, and relational dimensions related primarily to the influence of elected members and the hierarchical power of DASSs. Capturing experiential evidence and knowledge of service users and frontline practitioners, being clear about expected impacts and monitoring accordingly, and using recognized evaluation tools would provide further local evidence and enable better comparison and sharing across local authorities.