Background: In an effort to prevent continued increases in obesity and diabetes, in January 2014, the Mexican government implemented an 8% tax on nonessential foods with energy density ≥275 kcal/100 g and a peso-per-liter tax on sugar-sweetened beverages (SSBs). Limited rigorous evaluations of food taxes exist worldwide. The objective of this study was to examine changes in volume of taxed and untaxed packaged food purchases in response to these taxes in the entire sample and stratified by socioeconomic status (SES).
Methods and findings: This study uses data on household packaged food purchases representative of the Mexican urban population from The Nielsen Company's Mexico Consumer Panel Services (CPS). We included 6,248 households that participated in the Nielsen CPS in at least 2 mo during 2012-2014; average household follow-up was 32.7 mo. We analyzed the volume of purchases of taxed and untaxed foods from January 2012 to December 2014, using a longitudinal, fixed-effects model that adjusted for preexisting trends to test whether the observed post-tax trend was significantly different from the one expected based on the pre-tax trend. We controlled for household characteristics and contextual factors like minimum salary and unemployment rate. The mean volume of purchases of taxed foods in 2014 changed by -25 g (95% confidence interval = -46, -11) per capita per month, or a 5.1% change beyond what would have been expected based on pre-tax (2012-2013) trends, with no corresponding change in purchases of untaxed foods. Low SES households purchased on average 10.2% less taxed foods than expected (-44 [-72, -16] g per capita per month); medium SES households purchased 5.8% less taxed foods than expected (-28 [-46, -11] g per capita per month), whereas high SES households' purchases did not change. The main limitations of our findings are the inability to infer causality because the taxes were implemented at the national level (lack of control group), our sample is only representative of urban areas, we only have 2 y of data prior to the tax, and, as with any consumer panel survey, we did not capture all foods purchased by the household.
Conclusions: Household purchases of nonessential energy-dense foods declined in the first year after the implementation of Mexico's SSB and nonessential foods taxes. Future studies should evaluate the impact of the taxes on overall energy intake, dietary quality, and food purchase patterns (see S1 Abstract in Spanish).