The working paper released by the New Zealand Treasury challenges the argument according to which a tax on sugar-sweetened beverages (SSBs) could be the most effective strategy to fight obesity as it neglects the multiple dimensions linked to this burden. The main argument presented by the author shows that introducing a tax on SSBs will not necessarily mean significant reduction in calorie consumption by consumers and for a number of reasons.
The paper firstly argues that the health status of those responding to a price increase is generally unknown and higher responses may come from healthy consumers rather than the target population group. Moreover, surveys typically measure expenditures rather than consumption and its effects can be experienced after a period of time longer than the survey period.
The author also aims at demonstrating the importance of the substitution effect of imposing a selective tax. Indeed, substitution towards lower-priced SSBs could have harmful rather than beneficial effects. Another problem he underlines is that emphasis is often only placed on the own-price elasticity of demand for SSBs although substitution towards other non-taxed goods that are high in calories can also take place, reducing or even eliminating any direct reduction in the consumption of SSBs. To illustrate the importance of the substitution effect, the author uses a mathematical model designed to examine the effect of total calorie consumption of a selective tax, rather than simply the consumption of SSBs. The conclusions show that the substitution effect to other non-taxed commodities with relatively high calorie content is significant and that imposing a sugar tax does not necessarily mean lower calorie consumption for consumers.
Full paper can be found here