The opium wars, opium legalization, and opium consumption in China

"The effect of drug prohibition on drug consumption is a critical issue in debates over drug policy. One episode that provides information on the consumption-reducing effect of drug prohibition is the Chinese legalization of opium in 1858. In this paper we examine the impact of China's opium legalization on the quantity and price of British opium exports from India to China during the 19th century. We find little evidence that legalization increased exports or decreased price. Thus, the evidence suggests China's opium prohibition had a minimal impact on opium consumption"--National Bureau of Economic Research web site.