Hidden knowledge can occur in the accountability process if the accountor uses his superior procedural knowledge to reach the agreed output or outcome with less effort than the accountee assumes. If the accountor did not share his or her superior procedural knowledge, the whole division of labor would be
inefficient. A typical example is the often superior operating and project management knowledge of private partners in a public private partnership (e.g., Martimort & Pouyet 2006; Greiling 2009). As Benz discusses for EUpolicies, ex post room for maneuvering also emerges because the accountees often have limited competences and evaluate policies from the particular perspective of their organization or their constituencies (Benz 2007). Hidden action points to situations where the accountee cannot observe at all or only at prohibitively high costs all actions taken by the accountor. All mentioned ex ante and ex post information asymmetries in favor of the accountor are facilitated by the well-known evaluation problems of many public services. It begins with the problem that defining an achievable output and outcome is not an easy endeavor. Decades of experience with program evaluation and its myriad of problems regarding output and outcome measurement may serve as an illustration (Greiling 2006). Many public services are public because they have positive external effects, include non-contractible quality elements and are therefore difficult to measure (Gianakis 2002, 55).