Multi-objective decision-making for dietary assessment and advice

Unhealthy diets contribute substantially to the worldwide burden of non-communicable diseases, such as cardiovascular diseases, cancers, and diabetes. Globally, non-communicable diseases are the leading cause of death, and numbers are still rising, which makes healthy diets a global priority. In Nutrition Research, two fields are particularly relevant for formulating healthier diets: dietary assessment, which assesses food and nutrient intake in order to investigate the relation between diet and disease, and dietary advice, which translates food and nutrient recommendations into realistic food choices. Both fields face complex decision problems: which foods to include in dietary assessment or advice in order to pursue the multiple objectives of the researcher or fulfil the requirements of the consumer. This thesis connects the disciplines of Nutrition Research and Operations Research in order to contribute to formulating healthier diets. In the context of dietary assessment, the thesis proposes a MILP model for the selection of food items for food frequency questionnaires (a crucial tool in dietary assessment) that speeds up the selection process and increases standardisation, transparency, and reproducibility. An extension of this model gives rise to a 0-1 fractional programming problem with more than 200 fractional terms, of which in every feasible solution only a subset is actually defined. The thesis shows how this problem can be reformulated in order to eliminate the undefined fractional terms. The resulting MILP model can solved with standard software. In the context of dietary advice, the thesis proposes a diet model in which food and nutrient requirements are formulated via fuzzy sets. With this model, the impact of various achievement functions is demonstrated. The preference structures modelled via these achievement functions represent various ways in which multiple nutritional characteristics of a diet can be aggregated into an overall indicator for diet quality. Furthermore, for Operations Research the thesis provides new insights into a novel preference structure from literature, that combines equity and utilitarianism in a single model. Finally, the thesis presents conclusions of the research and a general discussion, which discusses, amongst others, the main modelling choices encountered when using MODM methods for optimising diet quality. Summarising, this thesis explores the use of MODM approaches to improve decision-making for dietary assessment and advice. It provides opportunities for better decision-making in research on dietary assessment and advice, and it contributes to model building and solving in Operations Research. Considering the added value for Nutrition Research and the new models and solutions generated, we conclude that the combination of both fields has resulted in synergy between Nutrition Research and Operations Research.</p

Social rationality, separability, and equity under uncertainty

Harsanyi (1955) proved that, in the context of uncertainty, social ratio- nality and the Pareto principle impose severe constraints on the degree of priority for the worst-off that can be adopted in the social evaluation. Since then, the literature has hesitated between an ex ante approach that relaxes rationality (Diamond (1967)) and an ex post approach that fails the Pareto principle (Hammond (1983), Broome (1991)). The Hammond-Broome ex post approach conveniently retains the separable form of utilitarianism but does not make it explicit how to give priority to the worst-off, and how much disre- spect of individual preferences this implies. Fleurbaey (2008) studies how to incorporate a priority for the worst-off in an explicit formulation, but leaves aside the issue of ex ante equity in lotteries, retaining a restrictive form of consequentialism. We extend the analysis to a framework allowing for ex ante equity considerations to play a role in the ex post approach, and find a richer configuration of possible criteria. But the general outlook of the Harsanyian dilemma is confirmed in this more general setting.risk, inequality, social welfare, ex ante, ex post, fairness, Harsanyi theorem

Optimal linear taxation under endogenous longevity

This paper studies the optimal linear tax-transfer policy in an economy where agents differ in productivity and in genetic background, and where longevity depends on health spending and genes. It is shown that, if agents internalize imperfectly the impact of genes and health spending on longevity, the utilitarian social optimum can be decentralized with type-specific redistributive lump sum transfers and Pigouvian taxes correcting for agents's myopia (leading to undersaving and underinvestment in health), and for their incapacity to perceive the effect of health spending on the resource constraint of the economy (causing overinvestment in health). The second-best problem is also examined under linear taxation instruments. Our main result is that it may be optimal to tax health spending, in particular under a complementarity of genes and health spending in the production of longevity.longevity, myopia, genetic background, social security, paternalism

Trading Off Generations: Infinitely Lived Agent Versus OLG

The prevailing literature discusses intergenerational trade-offs in climate change predominantly in terms of the Ramsey equation relying on the infinitely lived agent model. We discuss these trade-offs in a continuous time OLG framework and relate our results to the infinitely lived agent setting. We identify three shortcomings of the latter: First, underlying normative assumptions about social preferences cannot be deduced unambiguously. Second, the distribution among generations living at the same time cannot be captured. Third, the optimal solution may not be implementable in overlapping generations market economies.climate change, discounting, infinitely lived agents, intergenerational equity, overlapping generations, time preference

Allocating Students to Multidisciplinary Capstone Projects Using Discrete Optimization

We discuss an allocation mechanism of capstone projects to senior-year undergraduate students, which the recently established Singapore University of Technology and Design (SUTD) has implemented. A distinguishing feature of these projects is that they are multidisciplinary ; each project must involve students from at least two disciplines. This is an instance of a bipartite many-to-one matching problem with one-sided preferences and with additional lower and upper bounds on the number of students from the disciplines that must be matched to projects. This leads to challenges in applying many existing algorithms.We propose the use of discrete optimization to find an allocation that considers both efficiency and fairness. This provides flexibility in incorporating side constraints, which are often introduced in the final project allocation using inputs from the various stakeholders. Over a three-year period from 2015 to 2017, the average rank of the project allocated to the student is roughly halfway between their top two choices, with around 78 percent of the students assigned to projects in their top-three choices. We discuss practical design and optimization issues that arise in developing such an allocation

Utilitarianism and unequal longevities : A remedy?

This paper re-examines a counterintuitive corollary of utilitarianism under unequal longevities: the tendency to redistribute resources from short-lived towards long-lived agents, against any intuition of compensation. It is shown that this corollary prevails not only under time-additive lifetime welfare, but, also, in general, under non-additive lifetime welfare, so that this counterintuitive redistributive corollary is a robust argument against utilitarianism. This paper studies a remedy to that counterintuitive corollary. This consists in imputing, when solving the social planner's problem, the consumption equivalent of a long life to the consumption of long- lived agents. We identify the conditions under which such a modified utilitarian optimum involves a compensation of short-lived agents with respect to the laissez-faire. That remedy is also applied to an economy with risky longevity, where short-lived agents are penalized not only by the limited opportunities to spread resources over time (due to a shorter life), but, also, by lost savings (due to unanticipated death).utilitarianism, differential longevity, compensation, redistribution, consumption equivalent

Trading Off Generations: Infinitely-Lived Agent Versus OLG

The prevailing literature discusses intergenerational trade-offs predominantly in infinitely-lived agent models despite the finite lifetime of individuals. We discuss these trade-offs in a continuous time OLG framework and relate the results to the infinitely-lived agent setting. We identify three shortcomings of the latter: First, underlying normative assumptions about social preferences cannot be deduced unambiguously. Second, the distribution among generations living at the same time cannot be captured. Third, the optimal solution may not be implementable in overlapping generations market economies. Regarding the recent debate on climate change, we conclude that it is indispensable to explicitly consider the generations' life cycles.climate change; discounting; infinitely-lived agents; intergenerational equity; overlapping generations; time preference