Beverage purchases from stores in Mexico under the excise tax on sugar sweetened beverages: observational studyBMJ 2016; 352 doi: https://doi.org/10.1136/bmj.h6704 (Published 06 January 2016) Cite this as: BMJ 2016;352:h6704
- M Arantxa Colchero, researcher1,
- Barry M Popkin, professor2,
- Juan A Rivera, director3,
- Shu Wen Ng, associate research professor2
- 1Center for Health Systems Research, Instituto Nacional de Salud Pública, Universidad No 655 Colonia Santa María Ahuacatitlán, Cuernavaca, Morelos, Mexico
- 2Department of Nutrition and Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
- 3Nutrition and Health Research Center, Instituto Nacional de Salud Pública, Mexico
- Correspondence to: S W Ng
- Accepted 24 November 2015
Study question What has been the effect on purchases of beverages from stores in Mexico one year after implementation of the excise tax on sugar sweetened beverages?
Methods In this observational study the authors used data on the purchase of beverages in Mexico from January 2012 to December 2014 from an unbalanced panel of 6253 households providing 205 112 observations in 53 cities with more than 50 000 inhabitants. To test whether the post-tax trend in purchases was significantly different from the pretax trend, the authors used a difference in difference fixed effects model, which adjusts for both macroeconomic variables that can affect the purchase of beverages over time, and pre-existing trends. The variables used in the analysis included demographic information on household composition (age and sex of household members) and socioeconomic status (low, middle, and high). The authors compared the predicted volumes (mL/capita/day) of taxed and untaxed beverages purchased in 2014—the observed post-tax period—with the estimated volumes that would have been purchased if the tax had not been implemented (counterfactual) based on pretax trends.
Study answer and limitations Relative to the counterfactual in 2014, purchases of taxed beverages decreased by an average of 6% (−12 mL/capita/day), and decreased at an increasing rate up to a 12% decline by December 2014. All three socioeconomic groups reduced purchases of taxed beverages, but reductions were higher among the households of low socioeconomic status, averaging a 9% decline during 2014, and up to a 17% decrease by December 2014 compared with pretax trends. Purchases of untaxed beverages were 4% (36 mL/capita/day) higher than the counterfactual, mainly driven by an increase in purchases of bottled plain water.
What this study adds The tax on sugar sweetened beverages was associated with reductions in purchases of taxed beverages and increases in purchases of untaxed beverages. Continued monitoring is needed to understand purchases longer term, potential substitutions, and health implications.
Funding, competing interests, data sharing This work was supported by grants from Bloomberg Philanthropies and the Robert Wood Johnson Foundation and by the Instituto Nacional de Salud Pública and the Carolina Population Center. The authors have no competing interests. No additional data are available.
We thank Donna Miles for data management and programming support; Tania Aburto, Lilia Pedraza, Juan Carlos Salgado, and Emily Ford Yoon for research assistance; Frances L Dancy for administrative assistance; Mauricio Hernandez Avila; and our independent evaluation advisory committee, comprised of: Harold Alderman, Frank Chaloupka, Corinna Hawkes, Shiriki Kumanyika, Gonzalo Hernandez Licona, Luis Rubalcava, Carlos Aguilar Salinas, Sinne Smed, Mary Story, and Walter Willett. We also thank reviewers for their helpful comments. The Nielsen Company is not responsible for and had no role in preparing the results reported in this study.
Contributors: MAC was involved in the literature search, study design, and data analysis and interpretation. BMP was involved in the literature search, study design, and data collection and interpretation. JAR was involved in the literature search, study design, and data interpretation. SWN was involved in the literature search, study design, and data collection, management, analysis, and interpretation. All authors helped to write the manuscript. They had access to the data (including statistical reports and tables) in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. BMP and SWN are guarantors for this study.
Funding: This work was supported by grants from Bloomberg Philanthropies and the Robert Wood Johnson Foundation and by the Instituto Nacional de Salud Pública and the Carolina Population Center. The funders had no role in the study design or the analysis and interpretation of the data. All authors and their institutions reserve intellectual freedom from the funders.
Competing interests: All authors have completed the ICMJE uniform disclosure for at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and have declared funding sources, have had no financial relationships with any organizations that might have an interest in the submitted work in the previous three years, and have had no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: This study (No 14-0176) is exempt from approval by internal review board (reviewed by University of North Carolina at Chapel Hill office of human research ethics).
Data sharing: Owing to the proprietary nature of the main data source used for this analysis, the authors are contractually bound and unable to share the data.
Transparency: The lead authors (BMP and SWN) affirm that the manuscript is an honest, accurate, and transparent account of the study reported; that no important aspects of the study have been selectively omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.
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