"I only use low strength"

A lot of readers will have an answer ready here, which is that they're on a low strength. Six milligrams, or three. It's barely anything. The people with the problem are the ones on twenty.

Lynne Dawkins and colleagues tested this in 2016 with eleven experienced vapers. Each spent an hour vaping freely on two occasions, once with a six milligram liquid and once with twenty-four. With the low strength, they took more puffs, longer puffs, and got through about twice as much liquid. Their craving and withdrawal ratings at the end of the hour were the same in both sessions. They'd puffed their way up to the same comfort. The blood nicotine was still higher with the strong liquid, so the compensation wasn't complete, but it was enough to make them feel the same. The researchers called it self-titration, which means adjusting your own dose to a level, and it's been known in smokers for decades.

It was eleven people, all men, in a laboratory, so hold the numbers lightly. But the pattern is the one you'd expect from chapter 4. If the draw is there to reverse the fall, and the fall is a fall in nicotine, then your hand will keep reaching until the fall is reversed, however much or little nicotine each draw carries. A low strength doesn't lower the line. It raises the day's number.

So when you say you're only on six, what you're telling me is the number on the bottle, and the number on the bottle isn't the dose. The dose is the number on the bottle times the day's number, and you don't know the day's number, and if you're on six it's probably higher than you think. That's why I asked you to count before anything else. The bottle tells you almost nothing. The tally tells you what's happening.

There's a practical consequence, and it's in chapter 17. You can't bring the line down by strength alone, because your hand will make up the difference. You have to bring the strength and the number down together, and the number is the one to watch.