The main conclusion from these ordinary least square regressions is that the effect of college education in reducing smoking prevalence and increasing the probability of smoking cessation is robust even after controlling for gender, race, age, birth cohort, date of interview, and income. However, these results, if they allow us to conclude that the effect of education goes over and above the ability to generate an higher income, do not allow us to reject the hypothesis advanced by Fuchs (1982) that the fact that more educated individuals are less likely to smoke is due to selection on unobservables, like the discount factor.

Evidence from a plausibly exogenous variation in education would strengthen the argument that the effect of education in reducing smoking prevalence is causal. This motivates the implementation of an instrumental variable approach that exploits the fact that college attendance has been used as a draft avoidance strategy during the Vietnam War.<sup>22</sup>

# **_4.2 An Instrumental Variable Approach: College Attendance as a Draft Avoidance Strategy_**

During the Vietnam War, some males enrolled in college to avoid the draft. Card and Lemieux (2000; 2001), by contrasting enrollment for males and females and the deviations from the trend in male/female ratio, estimate that this effect increased college graduation rates for males by 2 percentage points. They construct a measure of the induction risk faced by each birth cohort of males: the average yearly number of inductions in Vietnam during the years when a particular birth cohort was aged 19-22 divided by the size of the birth cohort. Based on their paper, I have reconstructed this measure.<sup>23</sup> It is plotted in figures 7 and 8. Of course, for females, the induction risk is always zero.

This measure of the risk of induction is used as an instrument for the effect of college education on smoking prevalence in table 4, which contains the results from the first stage and instrumental variable regressions.<sup>24</sup> The format is the same as in table 3.

The first stage regressions in the upper part of table 4, indicate that the risk of induction is always positively and significantly correlated with college education, 22 In parallel research, Grimard and Parent (2003) develop a comparable strategy using a different data set. In their paper, which focuses exclusively on the strategy that uses the Vietnam draft as an instrument for college education, they define their instrument less precisely and obtain the result that education matters for smoking prevalence but not for smoking cessation. The latter result is somewhat surprising if one considers that, as argued in section 3, smoking cessation is the “cleaner” margin to look at the link between education and smoking, as the quitting decision is taken when schooling levels are definitive. They also exclude actual veterans from their sample in their main specifications.

23 The number of inductions per semester is from appendix table 1 in Card and Lemieux (2000). The size of the cohort is taken from United States Government (2000).

24 Notice that this instrument is different than the Vietnam-Era Draft Lottery used by Angrist and Krueger (1992). The draft lottery was in effect between 1970 and 1973, when the number of inductions was already declining.

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