Lechene, Valerie; Adda, Jerome - Department of Economics, Oxford University - 2004
according to some unobserved health characteristic, then estimates of the effect of tobacco on health that do not account for …. We show that there is selection into smoking, and considerable dispersion around the average effect, so that health … and nonsmokers will spuriously reveal a worsening effect of tobacco on health if they fail to control for selection. …