Adding the clinical framing, because it changes how the question reads. The distinction that resolves most of these threads is between what is true on average and what is true for one person. Both are real; they answer different questions and get quoted as if they were the same one.
If somebody has the primary source to hand I would rather cite it than paraphrase it.
sophie_paris said:The distinction that resolves most of these threads is between what is true on average and what is true for one person.
This matches mine closely enough to be worth saying so out loud.
sophie_paris said:The distinction that resolves most of these threads is between what is true on average and what is true for one person.
There is a second half to this that has not been said yet. It is worth asking what the claim would look like if it were false. If nothing would look different, it is not a claim about the world and no amount of discussion will settle it.
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Browse GL BiochemThe figures, for anyone assembling their own picture. One practical note: write down what you did and when, before you need it. Reconstructing a timeline from memory three months later is how people end up unable to answer the one question that would have resolved it.
A narrower follow-up, since the general answer is now clear:
How much of the between-person variation is pharmacokinetic and how much is just adherence measured badly?