Over the past few years adult use of e-cigs has been increasing while adult smoking has been declining. It is important to determine if there is a causal effect of e-cig use on smoking because of the known health hazards associated with smoking. An important concern with most prior studies of e-cigs and smoking is that endogeneity between e-cig use and cigarette use is ignored. One contribution of this paper is to instrument e-cig use in order to avoid this endogeneity problem. The data employed to estimate the empirical models come from the 2014-2015 Tobacco Use Supplements (TUS). The data employed in this study rely on the combined July 2014, January 2015 and May 2015 waves of the TUS. The results show that e-cig use increases the probability of a quit attempt, the probability of a quit failure and the number of quit failures. E-cig use is also found to reduce smoking by failed quitters and non-attempters. Past studies have shown that successful quitting may follow after a few years of e-cig use but the TUS is limited to a one year retrospective window, which may be too short to observe the causal effect of e-cigs on successful quit attempts. Although there is no evidence in the TUS regressions that e-cigs use affects the probability of a successful quit, the results for attempts, failures and reduction of smoking suggest that e-cigs create a path toward cessation.
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