Projects may be more successful if they are participatory in design and implementation.
A review of thirty completed World Bank projects from the 1970s found an average rate of return of 18% for projects that were judged culturally appropriate but only 9% for projects that did not include mechanisms for social and cultural adaptation. A more detailed study of fifty-two USAID projects similarly found a strong correlation between participation and project success, especially when participation took place through organizations created and managed by the beneficiaries themselves. Haiti's top-down afforestation programme did not meet its tree-planting targets. Then in 1981, NGOs helped provide trees that were selected by farm households. Instead of 3 million trees on 6,000 family farms originally planned, 20 million seedlings were planted on the farms of 75,000 families who voluntarily joined the programme. In the Philippines the National Irrigation Authority (NIA) used early involvement of community groups in planning construction and in finding ways to avoid the silting of channels and drains. This resulted in better maintenance of irrigation works and higher agricultural yields. A combination of community collection and centralized disposal has allowed Jakarta to achieve an 80% waste collection rate.