http://hdl.handle.net/10174/150 2026-04-03T18:32:12Z http://hdl.handle.net/10174/41194 Title: Fruit and Vegetable Consumption and Happiness in the United Kingdom, Australia, and South Africa: A Fixed Effect Instrumental Variable Analysis Authors: Chao, Li-Wei; Leite, Rui; Farias, Ana Rita; Ramlagan, Shandir; Peltzer, Karl Abstract: BACKGROUND: Fruit and vegetable (FV) consumption has been linked to better physical health. Recent studies also link FV consumption to better mental health. The World Health Organization (WHO) has recommended consuming at least five servings of FV per day, but recent statistics find most populations (in both developed and developing countries) achieve far below the target, despite knowing “FV is good for health”. Two recent studies using large survey data from Australia and from the U.K. using fixed effect (FE) regression found significant and large positive associations between FV consumption and life satisfaction; the authors caution that fixed effect regression cannot show causality. METHOD AND RESULTS: Using data from the U.K., Australia, and South Africa, we apply FE and instrumental variables (IV) regressions to show that the effect of FV on life satisfaction is plausibly causal. We use the consumer price index (CPI) of FV as the instrument (F statistic > 16). We test whether controlling for individual time invariant effects was necessary, by using correlated random effects as control functions; we find that controlling for time invariant effects is not necessary for the relationship between FV and life satisfaction. We further test whether the FV variable is endogenous after controlling for FE; we find FV remains endogenous even with FE. We calculate the elasticities of FV’s effect on life satisfaction and find similar elasticities across the three countries; the increase in life satisfaction from increasing average daily FV intake by one serving would more than offset the negative effect on mental health from becoming unemployed or developing a chronic illness. To explore whether the large effect size from IV estimates is due to heterogeneous treatment effect, we apply marginal treatment effect (MTE) estimation on WHO’s five-a-day recommendation. We find that the MTE curve is downward sloped: Although some may derive large gains in marginal utility by switching from not-meeting to meeting five-a-day, others may derive little gain. Examining the potential outcomes of meeting versus not meeting five-a-day (conditioning on the individual differences in observed and unobserved resistance to meeting WHO’s guideline), we find that anyone who meets the five-a-day derives a potential high life satisfaction -- regardless of the level of resistance to eating FV. The key difference lies in the individual differences in the potential outcomes when people consume low amounts of FV. Individuals with high resistance in achieving five-a-day still have relatively high life satisfaction despite not consuming five-a-day. However, individuals with low resistance in meeting five-a-day derive very low life satisfaction had they not consumed enough FV. DISCUSSION: A public information campaign to “educate” that people will be “happy” with more FV will likely be ineffective. This is because those who derive greater happiness with more FV consumption already have low resistance to treatment and thus already consume their five-a-day. Those who do not consume five-a-day also know they are just as happy eating versus not eating five FV servings a day, so the campaign to them is irrelevant. 2023-07-10T23:00:00Z http://hdl.handle.net/10174/41140 Title: Preference-Shifting Violence: Evidence From The Marikana Massacre Authors: Leite, Rui; Chao, Li-Wei Abstract: Objective: This study examines how the risk and time preferences of a sample of South African adults were affected by the Marikana massacre, a prominent episode of police violence that took place in South Africa on August 16, 2012. Previous studies have found that exposure to violence affects risk and time preferences (e.g., Voors et al., 2012; Jakiela & Ozier, 2019), but the direction of the effect is unclear. Our study contributes to this discussion and highlights a channel through which police violence – a sporadic but persistent phenomenon in many societies – can affect human decision making. Methodology: The Marikana massacre intersected fieldwork for the second wave of a large longitudinal survey being conducted in the Gauteng region, creating plausibly exogenous variation in respondents’ exposure to the event. We exploit this natural variation to estimate the causal effect of the exposure to violence on individual risk and time preferences using Pooled OLS regression models. To corroborate our findings, we examine how risk and time preferences relate to a proxy measure of interest in the Marikana massacre that is based on the intensity of internet searches for the term “Marikana”. We further test the robustness of our results by controlling for other contemporaneous events in South Africa that may act as confounding factors, and we address potential unobserved heterogeneity by re-estimating our models with individual and area-level fixed-effects. Originality: To the best of our knowledge, this study is the first to examine the impact of witnessing the Marikana massacre on risk and time preferences among South African adults. In contrast with prior research that examines long-run effects of violence on preferences or relies on retrospective recall, our design captures real-time behavioural consequences as the violent event and its aftermath unfold. We further contribute methodologically by using a measure of public salience of the event that relies on high-frequency internet search data to validate the timing-based identification strategy inherent in our natural experiment framework. Results: We find a statistically significant difference in risk and time preferences between individuals surveyed before and after the Marikana massacre, with individuals surveyed after the massacre being more risk seeking and having higher discount rates. Our pooled OLS estimates indicate that among respondents interviewed after the massacre, risk aversion and the discount rate both are higher of each standard deviation. Estimates from fixed-effects models that account for unobserved heterogeneity suggest that immediately after the massacre these effects are substantially larger. Practical implications: Out study provides strong evidence that witnessing a violent event alters risk and time preferences, two key determinants of a wide range of decisions – such as saving, investment, and health behaviour – that ultimately affect long-term welfare and development outcomes. If witnessing violence induces individuals to become more risk-averse or short-term oriented, this could reduce human capital accumulation, discourage entrepreneurship, or lead to unhealthy behaviour. From a policy perspective, our study thus highlights the broader developmental costs of police violence, and raises the possibility that such violence may contribute to widen inequality where minorities are disproportionately affected by police violence. 2025-07-03T23:00:00Z http://hdl.handle.net/10174/40484 Title: Expectations and Risk Attitudes: Evidence from a Longitudinal Survey in Tshwane, South Africa Authors: Leite, Rui; Chao, Li-Wei; Szrek, Helena; Pereira, Nuno Sousa Abstract: We investigate the relationship between risk taking propensity and economic and health expectations using data from a longitudinal survey conducted in the Tshwane Municipality, South Africa. We find that better economic expectations and better health expectations significantly predict higher risk taking propensity. We find that the results regarding economic expectations generalize under a variety of robustness checks, but the results regarding health expectations do not. Our findings highlight a channel through which economic expectations can affect decision making under risk. 2025-07-04T23:00:00Z http://hdl.handle.net/10174/40481 Title: Climate-related health risks and the willingness to pay for climate-change mitigation Authors: Coelho, Maria; Leite, Rui Abstract: Climate change is one of the main challenges of our time, and public support for mitigation policies often emphasizes environmental impacts. However, health impacts can also be substantial, raising the question of whether framing policies around health versus environmental effects influences support. This study examines whether policy support differs across these domains and how time preferences, risk aversion, and ambiguity aversion relate to willingness to accept climate-related tax increases. We recruited 134 adults in Portugal for an online survey collecting sociodemographic data, climate change attitudes, willingness to accept tax increases to mitigate health and biodiversity impacts and measures of risk, ambiguity, and time preferences. Time preferences were measured using a task based on Kirby et al. (1999), and risk and ambiguity aversion were jointly measured using a task based on Levi et al. (2010). We find no statistically significant difference in the distributions of the accepted tax increase to mitigate health effects of climate change and the accepted tax increase to mitigate biodiversity effects. Our results indicate that, across both domains, there is no statistically significant association between risk preferences and the willingness to accept tax increases to mitigate the effects of climate change. However, our findings suggest that those who are more ambiguity tolerant and more impatient are less willing to accept these same tax increases. This study contributes to the literature by examining how framing climate change in terms of health versus environmental impacts affects public support for mitigation policies. We find that individuals do not significantly differentiate between health and biodiversity outcomes, risk preferences play a minimal role, and higher ambiguity tolerance and impatience are negatively associated with willingness to support such measures. These results suggest that emphasizing health impacts, rather than environmental impacts, is unlikely to substantially change public acceptance of climate policies. 2025-09-18T23:00:00Z