Estimates of the costs of achieving intermediate or long-term global development goals are subject to uncertainties that go well beyond those in applied economic contexts, and exceed the level that is tolerable. It therefore seems inappropriate that such estimates should be relied on heavily to determine global resource mobilisation targets and priorities for action for lengthy planning horizons. Consequently, an alternative planning and resource allocation framework that is flexible and learning-oriented is needed. In this note, we explore one important class of reasons for uncertainties concerning the validity of recent estimates of the intermediate or long-term cost of achieving global goals, which stem from the unknown nature of the "development production function" and its (dual) cost function.
