That is pretty interesting! So, efficiency-wise, joints seem to rule over any kind of waterpipe or bong or vaporizer. They didn't test just normal pipes, but I'd think those would be the same as joints, minus the carcinogens of the paper. I notice they also said nothing about eating cannabis which, in my (admittedly limited) experience, is by far the most efficient way to consume cannabis.

My smoking is generally: normal pipe (titanium bowl, tube, and screen), with an occasional joint, and eating. So, I guess I'm about as efficient as it's possible to get in regards to my consumption. That explains why pot seems to last me a very long time, yet I am often baked. Heh.