Impact of the North American Free Trade Agreement on high-fructose corn syrup supply in Canada: a natural experiment using synthetic control methods

Abstract

BACKGROUND: Critics of free trade agreements have argued that they threaten public health, as they eliminate barriers to trade in potentially harmful products, such as sugar. Here we analyze the North American Free Trade Agreement (NAFTA), testing the hypothesis that lowering tariffs on food and beverage syrups that contain high-fructose corn syrup (HFCS) increased its use in foods consumed in Canada. METHODS: We used supply data from the Food and Agriculture Organization of the United Nations to assess changes in supply of caloric sweeteners including HFCS after NAFTA. We estimate the impact of NAFTA on supply of HFCS in Canada using an innovative, quasi-experimental methodology — synthetic control methods — that creates a control group with which to compare Canada’s outcomes. Additional robustness tests were performed for sample, control groups and model specification. RESULTS: Tariff reductions in NAFTA coincided with a 41.6 (95% confidence interval 25.1 to 58.2) kilocalorie per capita daily increase in the supply of caloric sweeteners including HFCS. This change was not observed in the control groups, including Australia and the United Kingdom, as well as a composite control of 16 countries. Results were robust to placebo tests and additional sensitivity analyses. INTERPRETATION: NAFTA was strongly associated with a marked rise in HFCS supply and likely consumption in Canada. Our study provides evidence that even a seemingly modest change to product tariffs in free trade agreements can substantially alter population-wide dietary behaviour and exposure to risk factors.

Vegetable intake frequency is higher among the rural than among the urban or suburban residents, and is partially related to vegetable cultivation, receiving, and purchasing at farmers’ markets: A cross-sectional study in a city within Gunma, Japan

“…It is difficult to implement interventions designed to increase the amount of vegetable production in a region and then evaluate whether the intervention affects the vegetable consumption practices or not. Presumably, a natural experiment 30 ) may be a promising research strategy in order to reveal the causal relationships.…”

Does trade liberalization reduce child mortality in low- and middle-income countries? A synthetic control analysis of 36 policy experiments, 1963-2005

“…The synthetic control method, developed by Abadie and colleagues, has been used extensively in analyses of social, political, and economic policies, including trade liberalization ( Abadie et al, 2010 ; Billmeier and Nannicini, 2013 ; Pieters et al, 2016 ; Rieger et al, 2017 ; Barlow et al 2017a , 2018 ). The synthetic control method is used to estimate the effect of an event or ‘treatment’, like trade liberalization, by approximating a counterfactual from a weighted combination of outcomes in similar countries.…”

“…It is also possible that trade reforms lead to widening wage differentials and worsen material conditions, especially among those working in import-competing sectors ( Krugman, 2008 ; Autor et al, 2013 ), thereby increasing child mortality by increasing inequality and reducing access to health sustaining goods and services among low-income groups ( Blouin et al, 2009 ). Finally, trade liberalization can increase harmful health behaviours such as tobacco and alcohol consumption among parents, thereby reducing children's health and longevity ( Friel et al, 2013 ; Barlow et al, 2017a ; Schram et al, 2017 ).…”

Toxic trade: the impact of preferential trade agreements on alcohol imports from Australia in partner countries

“…Because the ‘treatment’ of signing a PTA is non‐random, we cannot be confident that our estimate provides a good estimate of the impact of signing PTAs with other partners in the future. Future studies interested in doing so may wish to employ synthetic control methods, similar to work conducted in the area of trade and ultra‐processed food and beverages products or alcohol research more generally .…”