The Chilean State delivers essential meal services at schools for low-income students. Junta Nacional de Auxilio Escolar y Becas, the institution in charge of covering 1,300,000 children, leases the meal service to private enterprises. We developed an integer linear programming model to assign the meal contracts, in a process known as combinatorial auctions. The resulting model, which is NP-hard, led to significant improvements in efficiency and also contributed to making the process more transparent. The results are apparent in substantial improvements in quality and coverage of the service, and important savings to the country, which are equivalent to feeding 300,000 children in addition. We developed techniques to solve the combinatorial models and also to analyze and compare multiple scenarios to find robust solutions. For the objective function of this problem, we analyzed several options to consider different kinds of social benefits. In this paper, we describe the problem, the methodology and the results. We also present empirical results based on 6 years of experience. Finally, we discuss the relevance and impact of using operations research in these central issues in developing countries.

Chile's school system is using mathematical modeling to assign catering contracts in a singleround sealed-bid combinational auction. The Chilean state spends around US$180 million a year to feed 1,300,000 students from low income families, making this one of the largest state auctions. To improve the quality of the assignment in the auction process, we constructed an integer linear programming model to decide contract awards optimally among different concession holders. The model completely changed the nature of the process in three crucial aspects. First, it gave transparency and objectivity to the complete process, generating competition among firms. Second, it allowed the companies to build flexible territorial bids to include their scale economies, leading to efficient resource allocation. Finally, the model indeed found an optimal solution, which is not easy because the assignment problem was NPcomplete with more than 10,000 binary variables. This new methodology improved the pricequality ratio of the meals with yearly savings of around US$40 million-equivalent to the cost of feeding 300,000 children during one year. (Games/group decisions: bidding/auctions. Government: agencies.

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Background High-quality out-of-classroom interactions between students and teachers help to develop communities of learning. In medicine, they contribute to the professionalisation of students. Methods We designed a novel student-faculty lunch scheme for first year medical students at our institution. Students received a free lunch in groups of six, with a faculty member 'hosting' and paying for lunch with the cost reimbursed by the medical school. Focus groups with students were used to evaluate the impact of the intervention. Results Approximately half of all year 1 students signed up for the scheme (n=153). Twenty faculty members hosted one or more lunches. Focus group analysis revealed that attendees felt more positively about individual faculty and the institution as a result of participation, and that it helped the process of induction and transition into medical school, but that it suffered from a lack of ongoing contact. Conclusions This intervention encouraged positive student-faculty interactions, albeit with a relatively small group of students. However, it did not seem to encourage longitudinal staff-student relationships, a key limitation.