“…Despite the fact that these two phenomena often coexist-particularly among "sin goods"-they are usually examined in isolation. Empirical analyses of social interactions have examined their effect on alcohol (Kremer and Levy 2008), crime (Glaeser, Sacerdote, and Scheinkman 1996), disadvantaged youth (Case and Katz 1991), grades (Sacerdote 2001), obesity (Blanchflower, Van Landeghem, and Oswald 2009;Christakis and Fowler 2007;Fortin and Yazbeck 2015), and smoking (Fletcher 2010;Krauth 2007;Powell, Tauras, and Ross 2005). Prominent studies of addiction include Becker, Grossman, and Murphy (1994), Chaloupka (1991), Crawford (2010), Demuynck and Verriest (2013), and Gruber and Koszegi (2001).…”