Programmes to improve the productivity and welfare of the poor, who in many countries do not share even a common language with government administrators, have always posed special problems. Increasing concern about the cost and replicability of programmes is leading to greater involvement of beneficiaries in the construction, maintenance, and financing of local projects that hitherto either were provided and run by government or were simply unavailable. People-centred programmes are particularly hard to manage because of the degree of uncertainty involved. First, goals can be abstract ("community self-reliance", for example) and performance not quantifiable in terms of construction time and costs or profits and losses. Second, there is little knowledge of how to design suitable programmes, because they involve changing human behaviour patterns that vary among cultures and localities. Third, the success of a project depends on whether people want the services it offers: project managers therefore often have to create demand. The task of management is thus more one of experimenting and learning than of implementing known procedures, as is the case with physical development.