Substantial tobacco outlet reduction strategy
Travel costs (treated as an incremental increase in the price of a pack of 20 cigarettes)The incremental travel costs for intervention year 1 to 14 were calculated with a mathematical formula including three parameters16: (1) a monetary value on vehicle running costs per distance travelled (eg, fuel, car maintenance, but excluding insurance and depreciation cost; NZ$0.28/km), (2) a monetary value on time spent travelling (eg, personal non-work related travel time cost derived from NZ survey data; NZ$ 7.18/hour) and (3) an increasing proportional rate for the fraction of the total trip that was designated as tobacco purchase related (and hence the travel costs that could be apportioned to changes in access to outlets). To estimate the latter, the travel times for a return trip from the 1542 population-weighted neighbourhood centres to the nearest tobacco retail outlet for each year were divided into time categories with each an assigned proportion of the trip that was assumed to be tobacco related: <15 min (10%), ≥15 and <30 min (25%), ≥30 and <60 min (50%), ≥60 and <90 min (75%), and ≥90 min (100%). For each year, we then calculated the fraction of the ‘average trip’ that was tobacco-related ranging from 22% in year 1 to 56% in year 14.
The following formula was used to estimate incremental travel costs for each intervention year:
Xt=pt×(((0.28×Kt)+(7.18×Tt))–((0.28×Kt-1)+(7.18×Tt-1))), where Xt = net travel cost increase for each intervention year; p = the proportion of the travel costs explicitly for tobacco; 0.28 = the marginal running cost of a car per km; Kt = the kilometres travelled from the population-weighted centroid of the CAU to the nearest tobacco outlet; 7.18 = the monetary value of personal travel time per hour; Tt = the time spent travelling to the nearest tobacco retail outlet.
To estimate the overall uncertainty around incremental travel costs (ie, incremental increase in the additional indirect price of a pack of 20 cigarettes), uncertainties around the running cost of a car, the value on time spent in car for travel and the amount of travel explicitly for tobacco were mathematically combined in a single ‘total travel cost formula’. The formula was run a 1000 times with Monte-Carlo simulation for each intervention year in TreeAge software.
We assumed all three travel cost parameters would fall into the ‘more uncertain variables’ category (see ’Uncertainty and scenario analyses' in the main text). As such, an uncertainty with a log-normal distribution of ±20% SD around the running cost of a car was assumed. An uncertainty with a log-normal distribution of ±20% SD around the value on personal travel time was assumed. An uncertainty with a normal distribution of ±20% SD around the proportion of a trip being for the purchase of tobacco was assumed.
Total cost uncertainty log-normal distribution, ±25% SD. Uncertainty correlation 1.0 across yearly travel costs.
 Age-varying tobacco price elasticitiesAs per the tax increase strategy.As per the tax increase strategy.
In one scenario analysis, price elasticities were halved (yet still 20% higher age-varying price elasticities for Māori compared with non-Māori). In another scenario analsis, price elasticities were set the same for Māori and non-Māori.
 Illicit tobacco market dynamicsAs per the tax increase strategy.As per the tax increase strategy. In scenario analyses, we set the market share of the illicit market to remain at 1% (ie, a stable illicit market).