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Suladda Pongutta HPPU Journal Club

Suladda Pongutta HPPU Journal Club. Implications of sugar-sweetened beverages (SSB) tax when substitutions to non-beverage items are considered. Introduction. Proposed soda tax - another 1 cent/ounce 8-10% reduction in SSB consumption

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Suladda Pongutta HPPU Journal Club

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  1. Suladda Pongutta HPPU Journal Club Implications of sugar-sweetened beverages (SSB) tax when substitutions to non-beverage items are considered

  2. Introduction Proposed soda tax - another 1 cent/ounce 8-10% reduction in SSB consumption - increase SSB tax by 18% prevent 145,000 adult-obesity cases Argument - If this can prevent sweet-addicted people from searching for substitutes Fail to raise SSB tax

  3. Introduction GAPS of knowledge • Prior studies did not control for potential price endogeneity. • Prior studies did not take other possible substitutions into account. (apart from beverage family) • If the switches increase consumption of sodium and fat?

  4. Objectives • To predict the effects of the proposed rate of SSB tax, when considering other possible substitutions, on - energy consumption and body weight - fat & sodium consumption

  5. Data management Purchase record; payment + units + socio-demographic (Nielsen Homescan panel) Nutrition info. (Glandson 2009 & USDA) SSB; soda, fruit drinks, sport energy Other bevs; ; fruit juices, milk, diet soda food; candies, cookies, salty snacks, ice cream, yogurt, ready-to-eat cereal, french fries, pizza, frozen dinners, caned fruits & vegetables & soups. data in 2006 Q1 Q2 Q3 Q4 28,584 households 114,336 individuals (> 6 yrs old.)

  6. Data analysis Each food item 1 Disaggregate regression Instrumental variable model, IV Exogenous model 2 If 20% price increase has any effects on…… • Fat intake • Sodium intake • Energy intake • Body weight • Fat intake • Sodium intake • Energy intake • Body weight 3

  7. Exogenous models • Two part models of GLM family were used to deal with the skew of purchasing data • Aggregate regression was run to check the robustness of the total change of nutrient purchased

  8. Instrumental variable models • Variables - x; log of price index of SSBs (created by instrumental variable model) - y; fat & sodium & energy intake - control; log of price index of other food items, household per capita income, proportion of adults, ID of 52 Nielsen markets, socio-demographic characteristics. Control biases when creating instrument (price index) - weighted price index by using inverse of Euclidian distances between neighbors - excluded prices of HH living in the same tract to avoid common tract-specific demand shock

  9. Instrumental variable models • Models to estimate the effect - two-stage residual inclusion instrumental variable approach - estimate the effect of 20% price increase by using the incremental variations of nutrients purchased derived from the model mentioned earlier - convert the estimated reductions in calories into weight loss (alternative method, up to age, gender, fat & lean composition) • Quantile regression to assess the effect of tax on 25th , 50th , 75th percentiles of purchase (created instrument using the same model)

  10. Results Overall • SSBs taxes reduced daily store-bought energy by 21.2 (exogenous) and 13.2 kcal (IV) • slightly decreased fat intake (-21 & -26 cg/day; respectively) • Decrease sodium intake 10 (exogenous) & 6.8 mg/day (IV) but the effect was vague when running IV Disaggregated effects (IV) • Lower energy was mostly from lower consumption of soda (-5.5 kcal/day) and fruit drinks (-7.0) • The major substitute was fruit juices (+2.5 kcal/day) • Only food substitute was canned soups

  11. Results Disaggregated effects (IV) • Energy intake from salty snacks and ice cream decreased with lower energy from SSBs (-6.3 & - 4.8 kcal, respectively) and were the major contributors driving fat intake down • The major contributors of downward trend of sodium intake were soda (-1.6 mg/day), fruit drinks (-3.9 ), candy (-1.9) and ice cream (-1.6) while increasing consumption of canned soup increased sodium intake by 14.7 mg/day

  12. Results Arc-elasticity From energy to body weight • 24.3 kcal/day = 1.6 pounds in the 1st year or 2.9 pounds in the 10th year Big fans of SSBs and higher-energy consumers had lower price- elasticity but incremental change was high enough to cut their weights off -1.40 - 4.47 Q1 Q4

  13. Discussion • Data from purchasing survey were self-reported • The energy got from the 19 food categories accounted for only 518 kcal/day • Disadvantage; did not account for the income effect but the effect seemed to be limited • Advantages; • Nutrient purchased at the product level • Prevent endogeneity and measurement error

  14. Conclusion • Tax SSBs decrease energy and fat intake • No substitutions except for fruit juices and canned soups • Tax SSBs for 20% price increase may decrease unhealthy diet consumption and BW • SSBs tax proposed by this study seemed to be regressive but the effect can be reduced by performing sale tax • To tax SSBs, potential cost must be weighted against benefits • The taxes should be used in health promotion to gain more effect

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