On the Identi¯cation of the E®ect of Smoking on Mortality J¶erôme Adda¤and Val¶erie Lecheney

This paper considers the identi¯cation of the e®ect of tobacco on mortality. If individuals select into smoking according to some unobserved health characteristic, then estimates of the e®ect of tobacco on health that do not account for this are biased. We show that using information on mortality, morbidity and smoking, it is possible to control for this selection e®ect and obtain consistent estimates of the e®ect of smoking on mortality. We implement our method on Swedish data. We show that there is selection into smoking, and considerable dispersion around the average e®ect, so that health policies that aim at decreasing smoking prevalence and quantities smoked might have less e®ect in terms of average number of years of life gained than previously estimated. We also empirically show that selection into smoking has increased over the last ¯fty years with the availability of information on the dangers of smoking, so that future studies comparing smokers and non smokers will spuriously reveal a worsening e®ect of tobacco on health if they fail to control for selection. JEL number: I1