A key rationale for drug prohibition is the belief that outlawing drugs makes them less available and more expensive, thereby shrinking consumption.
Decades of evidence, however, suggest this impact is modest, partly due to the “waterbed effect”: enforcement efforts aimed at shrinking the market mainly cause it to shift, in various ways, without much impact on its overall size. Just as pushing down on one part of a waterbed merely forces the water somewhere else, rather than reducing the overall quantity.