procurement contracts funded by World Bank development aid. ("High-risk" tenders are those with a higher degree of World Bank oversight and control; as a result, the study authors noted that "our findings are not representative of all aid spending financed by the World Bank, but only that part where risks are higher" and more stringent oversight thus deemed necessary.) The study authors found "that donor efforts to control corruption in aid spending through national procurement systems, by tightening oversight and increasing market openness, were effective in reducing corruption risks." The study also found that countries with high party system institutionalization (PSI) and countries with greater state capacity had lower prevalence of single bidding, lending support for "theories of corruption control based on reducing opportunities and increasing constraints on the power of public administrators." A 2018 study published in the Journal of Public Economics investigated with Chinese aid projects in Africa increased local-level corruption. Matching Afrobarometer data (on perceptions of corruption) to georeferenced data on Chinese development finance project sites, the study found that active Chinese project sites had more widespread local corruption. The study found that the apparent increase in corruption did not appear to be driven by increased economic activity, but rather could be linked to a negative Chinese impact on norms (e.g., the legitimization of corruption). The study noted that: "Chinese aid stands out from World Bank aid in this respect. In particular, whereas the results indicate that Chinese aid projects fuel local corruption but have no observable impact on short term local economic activity, they suggest that World Bank aid projects stimulate local economic activity without any consistent evidence of it fuelling local corruption." Changed consumption patterns Food aid that is relatively inappropriate to local uses can distort consumption patterns. Food aid is usually exported from temperate climate zones and is often different than the staple crops grown in recipient countries, which usually have a tropical climate. The logic of food export inherently entails some effort to change consumers' preferences, to introduce recipients to new foods and thereby stimulate demand for foods with which recipients were previously unfamiliar or which otherwise represent only a small portion of their diet. Massive shipments of wheat and rice into the West African Sahel during the food crises of the mid-1970s and mid-1980s were widely believed to stimulate a shift in consumer demand from indigenous coarse grains – millet and sorghum