Demand reduction refers to efforts aimed at reducing the public desire for illegal and illicit drugs. The drug policy is in contrast to the reduction of drug supply, but the two policies are often implemented together. Some discussions of demand reduction make a distinction between policies that address single issues (such as public "knowledge-of-harms") or are short-term interventions(in-school programs), and those that approach drug demand as a complex issue with multiple social risk factors. Some economists such as Milton Friedman argue that due to the law of supply and demand, reducing demand is the only effective way to reduce drug use long-term. It is questionable, however, whether demand reduction programs actually reduce demand.