Table 3

Goodness of fit of the model with true IQOS introduction months versus placebo models (controlling for household income and seasonality)

introduction date model R2
Simultaneous mational-level placebo date models
– R2 distribution
Months testedMean R2 Top 10%Top 5%Max
Approach True introduction date model R2 Exact permutation test: true model and placebo dates – R2 distribution
True model rank Permutation count Significance level Top 10% Max
  • For the simultaneous national-level placebo dates, n=47 (48 months in the dataset minus the first month). The larger the R2 value the better the model fits. Ordering the models by the Akaike’s information criteria and Schwarz’s Bayesian information criteria yielded the same results. Month-of-the-year dummies are included in the models to control for seasonality. The regional monthly household income measure is the population-weighted average of the incomes in the prefectures in each region, adjusted for inflation. The Japan Statistical Office is the source for the average monthly household income and monthly inflation data.