Research

Solo-authored.

Abstract: In February 2023, Costa Rica reformed its basic value-added tax basket on which a reduced rate applies to “guarantee a balanced diet”. This paper assesses ex-ante the impact of the reform on nutrient availability and household spending across income groups. Price elasticities are estimated using pooled National Household Income and Expenditure Survey data and a two-step censored quadratic almost ideal demand system model accounting for price and total expenditure endogeneity. Nutritional information is derived from food composition tables. Food items are grouped by processing level as a proxy to explore differences in own- and cross-price effects between ‘healthier’ and ‘less healthy’ items. The demand for ultra-processed sweet and savoury foods is price-inelastic (-0.74 and -0.81, respectively). Lower-income households’ demand is more price-sensitive. The reform applies a reduced rate to a significant number of ultra-processed savoury food items and is associated with an increase in household purchases of calories (0.7%), sugar (0.4%), and saturated fat (1.2%). A counterfactual scenario with a basic tax basket defined based on the Pan American Health Organization nutrient profile model criteria is associated with the largest reductions in calories (-0.2%), sodium (-1.0%), and saturated fat (-0.6%), with higher benefits for lower-income households. It results in minor decreases in household spending (-0.2%). While an increasing number of countries contemplate the taxation of foods high in fat, salt, or sugar, Costa Rica is unique in mandating the consideration of nutritional aspects in determining value-added tax rates. However, the recently adopted basic tax basket may not fulfil this potential. 

Seminar presentations: University of Birmingham (Centre for the Economics of Obesity); University of Costa Rica (School of Economics, School of Nutrition); Imperial College London (Centre for Health Economics & Policy Innovation; Public Health Policy Evaluation Unit)
Conference presentations: Quantitative Methods in Social Sciences conference (University of Warwick, 2023); Sugar and Calorie Reduction Network 3rd meeting (UK Department of Health and Social Care & World Health Organization, Regional Office for Europe, 2025).

Dissemination materials: Slides; Twitter/X thread; Spanish abstract
Media: IB Knowledge

Co-authored with Laure de Preux (Imperial College London).
Link to paper (version May 2024): https://dx.doi.org/10.2139/ssrn.4862789  

Abstract: Amid the current syndemic of obesity and climate change, little is known about the effect of extreme temperatures on dietary behaviour. Using exogenous daily variations in weather and a nationally representative consumer panel in the U.S., we find that extreme heat increases the volume purchased of sugary drinks, with persistent impacts after accounting for inter-temporal purchase shifts. We explore heterogeneous effects and a range of potential drivers, including changes in shopping habits, inter-channel substitutions, retailers' price adjustments, and psychological biases. Results reveal higher impacts among the most vulnerable households and no evidence of long-run adaptation by historical heat exposure. We combine our estimates with output from climate models for 2080-2099. Our projections indicate that climate change may increase sugary drink purchases.

Seminar presentations: Imperial College London (Economics & Public Policy)
Conference presentations: Agricultural and Applied Economics Association (AAEA 2024); Association of Environmental and Resource Economists (AERE 2024); European Association of Environmental and Resource Economists (EAERE 2024); European Health Economics Association (EuHEA 2024); Sustainable Food Systems Symposium (University of Gottingen, 2024); French Economics Association (AFSE 2024); Canadian Economics Association (CEA 2024); Maastricht Workshop on Applied Economics of the Environment (MAEE 2024)

Revise & resubmit to PLOS Medicine as of September 2025.

Co-authored with Jingmin Zhu* (Imperial College London), Jack Olney (Imperial College London), Daniel J Laydon (Imperial College London), William Joe (IEG, New Delhi), Manika Sharma (RTSL, New Delhi), Lindsay Steele (RTSL, New York), and Franco Sassi (Imperial College London).
* We both share first authorship.

Link to paper (version March 2025): https://doi.org/10.1101/2025.03.06.25323478   

Abstract: Consumption of foods high in fat, sugar, and sodium (HFSS) and obesity are rapidly increasing in India. Taxing HFSS foods has been proposed to promote healthier diets. This study estimates the effect of this approach on nutrient intake, diet-related disease, and associated health and economic burdens. We use nationally representative household expenditure survey data, dietary requirements, and food composition tables to model individual nutrient intake. Consumer responsiveness to food price changes for three income terciles, captured in price elasticities, is estimated using an Almost Ideal Demand System model. Longer-term policy impacts are estimated through a novel dynamic microsimulation model, Health-GPS. Modelled policy outcomes include changes in risk exposures, disease incidence and burden, and total health expenditure. On average, 9.9% of total energy intake comes from HFSS items, as defined by the Food Safety and Standards Authority of India. Applying the current highest Goods and Services Tax (GST) rate of 40% on HFSS items is associated with a persistent average per capita decrease of 0.1705kg/m2 (95% CI: -0.1709, -0.1700) in body mass index and 45.8mg (95% CI: -45.9, -45.7) in daily sodium intake. Over 30 years, this could reduce annual disease incidence by up to 1.72% (95% CI: -1.78%, -1.66%) on average and prevent 0.63 million (95% CI: -0.71, -0.55) disability-adjusted life years per year from ischemic heart disease, chronic kidney disease, stroke, diabetes, and asthma, reducing total health expenditure by US$601 million (95% CI: -624, -578) per year. Further work is needed to incorporate potential benefits or harms associated with changes in other foods and nutrients that are not currently modelled, such as fruits, whole grains, fibre, and red and processed meats. Larger absolute health gains accrue to higher-income individuals, reflecting higher baseline HFSS food intake. Given substitution patterns and a price-inelastic demand, the tax change is expected to generate a 92.0% (95% CI: 88.2%, 95.7%) increase in tax revenue from foods and beverages with only a minor effect on household spending. Higher taxation of HFSS foods could help mitigate rising incidence of diet-related diseases and morbidity in India, reduce healthcare costs, and serve as an additional source of revenue for the government. 

Seminar presentations: Institute for Economic Growth (New Delhi, 2023)
Conference presentations: International Congress of Nutrition (IUNS-ICN, Paris, 2025); Delivering for Nutrition in South Asia (IFPRI, Kathmandu, Nepal, 2023)

Work-in-progress (IFPRI Discussion paper to be released in Oct 2025).
Co-authored with Andrew Comstock (IFPRI) and Olivier Ecker (IFPRI).

Abstract: Understanding how food demand responds to household income and price changes is essential for anticipating global food needs and designing effective food policies. Yet existing elasticity estimates vary widely due to differences in data, estimation methods, and study settings. This study aims to assess how empirical choices influence elasticity values and examine theory-based predictions related to income growth and inequality, urbanization, and demographic change. It provides the most comprehensive global systematic literature review and meta-analysis of income and price elasticities to date, compiling over 13,000 elasticity estimates from 215 peer-reviewed studies published between 1974 and 2022. We estimate two-level random effects meta-regressions and use the results to generate predicted elasticities for nine food groups by world region. While most data and methodological choices have little effect on price elasticity estimates, income elasticities are influenced by factors such as demand model type, use of conditional specifications, and the choice of expenditure measure. We find empirical support for Engel’s Law but only partial support for Bennett’s Law. Income elasticities are positively associated with urbanization, particularly in lower-income countries, and negatively associated with population aging. By projecting income elasticities through 2050 under alternative Shared Socioeconomic Pathways, we show that ignoring structural shifts in sociodemographics can yield meaningfully different estimates of future food demand.

Seminar presentations: International Food Policy Research Institute (IFPRI, forthcoming); Imperial College London (Centre for Health Economics & Policy Innovation)

Work-in-progress. Solo-authored.

Seminar presentations: Imperial College London (Economics & Public Policy)
Conference presentations: American Economic Association annual meeting (ASSA 2026, forthcoming); European Association of Agricultural Economics congress (EAAE 2025); Association of Environmental and Resource Economists (AERE, 2025); Potsdam Institute for Climate Impact Research (PIK)'s DENeB PhD Workshop 2025; Interdisciplinary PhD Workshop in Sustainable Development (Columbia University, 2025).