The promise of finding long-term technological solutions to the problem of world food shortages seems difficult to fulfill. Many innovations that were once heavily supported and publicized, such as fish-protein concentrates, have since fallen by the wayside. The proposals themselves were technically feasible, but they proved to be economically unfeasible and yielded food products culturally unacceptable to their consumers. Recent innovations such as opaque-2-maize, Antarctic krill (磷虾群), seem more promising, but it is still too early to predict their ultimate fate. One characteristic common to unsuccessful food innovations has been that, even with extensive government support, they often have not been technologically adapted or culturally acceptable to the people for whom they had been developed. A successful new technology, there fore, must fit the entire socio-cultural system in which it is to find a place. Security of crop yield, practicality of storage and costs are much more significant than had previously been realized. But the protein quality in tortillas made from opaque-2-maize will be of only limited benefit to a family on the margin of subsistence if the new maize is not culturally acceptable or is more vulnerable to insects. The adoption of new food technologies depends on more than these technical and cultural considerations; economic factors and governmental policies also strongly influence the ultimate success of any innovation. Economists in the Anglo-American tradition have taken the lead in investigating the economics of technological innovation. Although they exaggerate in claiming that profitability is the key factor guiding technical change -- they completely disregard the substantial effects of culture -- they are correct in stressing the importance of profits. Most technological innovations in agriculture can be fully used only by large landowners and are only adopted if these profit-oriented business people believe innovations that carry high rewards for big agri-business groups will be adopted even if they harm segments of the population and reduce the availability of food in a country. Since Large segments of the populations of many developing countries are close to the subsistence margin and essentially powerless, they tend to be the losers in this system unless they are aided by a government policy that takes into account the needs of all sectors of the economy. Therefore, although technical advances in food production and processing will perhaps be needed to ensure food availability, meeting food needs will depend much more on equalizing economic power among the various segments of the populations within the developing countries themselves. The primary purpose of the passage is to discuss ______.