Calls for increases in aid to achieve the Millennium Development Goals (MDGs) tend to assume a straightforward relationship between the volume of aid and the rate of development, says a paper from the Center for Global Development, which cites evidence which suggests that there is a weak link between the volume of aid and the rate of development, and highlights the often overlooked assumptions upon which costings of the MDGs are based. The authors warn that the MDGs may run the risk of creating an unwarranted climate of pessimism about development and aid and lead to reductions in aid.