Out of What Bodily Orifice Did He Pull That Figure? Part II

I've been looking for a source for Luis Suarez-Villa's claim that free trade in opium “caused far more deaths over time than Mao's revolution and his regime ever did.” I can't find any. Since Professor Suarez-Villa is a published author I tried googling his books. I found only one mention of opium, a reference to Auto Opium: A Social History of American Automotive Design by David Gartman, which does not sound very relevant to the present discussion.

In other words, [CITATION NEEDED].