In terms of substitution effects, the major difference between our estimates and those from the US is that our data indicate that diet soft drinks are a
substitute for
sugar sweetened drinks, whereas US data suggest that diet soft drinks are a complement (
as the price of
sugar sweetened drinks goes up,
consumption of diet drinks goes down).18 22 This may explain why a US tax on
sugar sweetened drinks has been so heavily resisted,
as a «double whammy» on sales of both diet soft drinks and
sugar sweetened drinks would occur.18.