Afe 1958 na Mensah kɔyɛɛ adwuma wɔ United Nations Secretariat wɔ Centre for Development Planning, Projections and Policies, wɔ New York City, a ɛwɔ Amerika. Mensah san baa Ghana 1961 bɛyɛɛ National Planning Commission daanonin.National Planning commission na ɛhyehyɛ san de deɛ yɛfrɛ no ɔman Seven-Year Development Plan (1963/64–1969/70). Afe 1969 na wɔyii no mmarahyɛni na ɔbɛyɛɛ fotosanfoɔ wɔ Busia aban mu kɔsii 1972 a Ignatius Kutu Acheampong sogya aban bɛsesaa no.