Gustav Feichtinger’s research while affiliated with University of Vienna and other places

We propose a theoretical model to study individual lifestyle choices related to calorie intake and physical activity, depending on personal fitness level and body weight. The model builds on the rational eating literature and can generate a variety of behaviors that are consistent with the empirical evidence. In particular, we show that engaging in periods of a sedentary lifestyle can be a rational, utility-maximizing decision-a finding that is not present in the existing literature but is empirically widespread. Additionally, we show the possible existence of multiple equilibria and multiple indifferent lifestyles. The former justifies policy interventions to help individuals exit a self-reinforcing, but unhealthy equilibrium; the latter provides a theoretical basis for remediation plans that compensate for earlier unhealthy behaviors. JEL codes: I10, D91 Summary The global rise in obesity is a major public health concern that has been attributed to individual traits like impatience and time preferences, market forces that affect food affordability and availability, and social factors such as peer effects, social contagion, and evolving norms about body image. Health economic theories suggest that lifestyle choices, including unhealthy behaviors, may result from rational intertemporal decision-making, where individuals weigh the present and future costs and benefits of their actions. Consequently, policy interventions addressing obesity have included taxation on calorie-dense foods and sugary drinks, incentives for physical activity, and educational campaigns promoting healthier lifestyles. Despite extensive research on eating behavior, economic studies have paid comparatively less attention to physical activity. The World Health Organization (WHO) emphasizes the importance of regular exercise, recommending at least 150 minutes of activity per week for weight management and overall health. However, adherence to these guidelines remains low, with over 80% of adolescents and 27% of adults failing to meet the recommended levels. This has long-term consequences for individual health and places financial strain on healthcare systems. This paper introduces a theoretical model exploring the interaction between rational eating and exercise decisions. It accounts for various lifestyle patterns and examines how body weight and physical activity evolve based on individual time and budget constraints. We show that three possible types of steady state can emerge: (1) an optimal weight with unrestricted eating and excessive exercise, (2) an overweight state with dietary restrictions and overexertion, and (3) an underweight state with excessive food consumption. The model also shows that, under certain conditions, adopting a sedentary lifestyle can be a rational choice. While inactivity may not be optimal over an entire lifetime, it can be an economically justified decision during specific periods. This finding aligns with empirical observations of individuals alternating between sedentary phases and active engagement in physical exercise. The cyclical nature of these behaviors resembles patterns seen in dieting and overeating. The paper introduces the notion of "Indifferent Lifestyles," referring to different life trajectories that yield the same long-term utility despite following distinct paths. This provides a theoretical foundation for delayed health investments, contingent on the ability to commit to future corrective actions. Accordingly, individuals may postpone healthy behaviors and still achieve similar long-term health outcomes if they can precommitt to later compensate for previous unhealthy choices. To choose among indifferent lifestyles, we propose a novel selection criterion based on the fact that, although these trajectories offer the same utility over an infinite time horizon, they can be ranked over finite time horizons. The model also provides insights into policy effectiveness. The impact of pricing interventions on food and exercise-related choices depends on an individual's initial health status. In cases where multiple equilibria exist, individuals may be unable to transition to a healthier state without external intervention. Additionally, small price changes can sometimes trigger substantial shifts in behavior rather than gradual adjustments, due to the presence of bifurcation points and regime switches. This 2 finding challenges the assumption that policy effects are always proportional and suggests that, in some cases, minor policy changes can lead to drastic behavioral responses. Overall, this research contributes to the economic analysis of obesity by integrating physical activity into rational choice models and exploring the conditions under which individuals may adopt different health-related behaviors. The findings have important implications for policymakers, suggesting that interventions should account for the interdependence between eating and exercise decisions. 3

We consider a resource extraction model with the possibility of extending the resource stock by drilling efforts and an oligopolistic competition of symmetric firms. Assuming a hyperbolic market demand, we adopt the open-loop Nash equilibrium to analyze and compare the outcomes of a private vs a common resource pool. For both cases, the drilling efforts of the individual firms strongly depend on the market structure. For a low competition, the efforts increase the number of firms, and the opposite is true for a high competition. On the other hand, aggregate drilling efforts are different among the two types of pools and are opposite to Schumpeterian's hypothesis (i.e., they are either an inverted U-shaped (private pools) or strictly increasing (single pools)).

We present and analyze a life cycle model of a scientific career to investigate how the budget available for research related activities affects a scientist’s long run success in academia. Recognizing that reputation has a positive impact on obtaining research funds as well as on producing scientific output, we determine the optimal efforts of a scientist with respect to applying for research grants and costly science related activities to improve reputation, such as networking and inviting guest researchers, under the assumption that the total extent of these activities is limited by a time budget. We find that the optimal solution is history-dependent and study four different career paths which differ with respect to the initial reputation and the initial financial means to identify the determinants of success and failure in academia. It is shown that the extent to which a scientist finds the results of his or her work rewarding, has a substantial impact on whether the scientist will build up a successful career.