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22. The conclusion in this argument is that increased vigilance by drug enforcement authorities has resulted in an increase in the illegal use of cocaine. The author reaches this conclusion on the grounds that drug traffickers have responded to increased enforcement efforts by switching from bulkier and riskier drugs to cocaine. Presumably, the authors reasoning is that the increased enforcement efforts inadvertently brought about an increase in the supply of cocaine which, in turn, brought about the observed increase in the illegal use of cocaine. This line of reasoning is problematic in two important respects. In the first place, the author has engaged in after this, therefore because of this reasoning. The only reason offered for believing that the increased vigilance caused the increase in cocaine use is the fact that the former preceded the latter. No additional evidence linking the two events is offered in the argument, thus leaving open the possibility that the two events are not causally related but merely correlated. This in turn leaves open the possibility that factors other than the one cited are responsible for the increase in cocaine use. In the second place, the author assumes that an increase in the supply of cocaine is | 
