text: tumultuous years of the 1980s, it was not only Governments in Africa that chanqed their policies and perspectives but also major multilateral institutions. The recent focus on the lonq-term structural constraints on development -such as papulation qrowth, human-resource development, environmental rehabilitation, food security and appropriate technoloqv -is not a hasty leaP into the void but a result of a slow, painstakinq review and reconsideration of simple but reassurinqly certain, earlier-held views on develoPment. The 1980s tauqht us all a little humili tv in the sense that all possible alternatives and approaches have had to be re-examined in the liqht of fresh problems and the need to broaden the basis of development. First, there is an unquestioned need to take a comprehensive approach to the problem of the economic reqeneration of developinq economies. The most fundamental concept with reqard to economic qrowth in those societies is that qrowth must be sustainable, that it should not be a fitful or intermittent process open to fortuitous international or ices or swinqs of weather but an accretionary advance towards enlarqinq domestic productive caoaci ty and improvinq resource allocation. However, as has been known since the early oost-war years, to enter into the virtuous spiral of self-sustaininq qrowth requires a minimum set of interlockinq and comPlementary economic activities that can be acquired only by a determined diversification o:E the production base. That, in turn, requires the raisinq of investment ratios to over 25 per cent of q ross cbmestic product, a pre-condition that is currently beinq met by several newly industrializinq economies hut not by a sinqle economy in sub-Saharan Africa. JB/17 A/S-18/PV. 6 77 (Mr. Ejiqu, Ethiopia) The idea of some critical minimum threshold of investment as a sine qua non of sustainable economic qrCMth is absolutely crucial to our understandinq of qrO!rJth processes in develoPinq economies, since it provides a convincinq explanation of 
analysis: The text discusses the challenges of economic development in sub-Saharan Africa, highlighting the need for sustainable economic growth, diversification of production, and increased investment ratios. It also touches on the importance of considering long-term structural constraints, such as population growth and environmental rehabilitation, in development strategies. The text's focus on economic growth, development, and investment suggests that it is primarily concerned with economic development, although it does touch on environmental and population-related issues.