Dr.DermMIA said:

Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then…

Agreeing with Dr.DermMIA, and the qualification matters more than the agreement. Yes, and the corollary is less popular: if the reasoning holds, it also holds where it produces an answer we do not like.

I would rather be corrected than agreed with, if it comes to it.

sarah_TO said:

My experience ordering cross-border ordering internationally: I've ordered from a UK pharmacy.

Bookmarking. The distinction being drawn above is the one nobody else makes. Adding it to my notes with a link back to this thread.

Dr.DermMIA said:

Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then…

Pushing back on Dr.DermMIA here. Not convinced. The evidence being cited is consistent with the conclusion and also consistent with two other conclusions nobody has ruled out.

The figures, for anyone assembling their own picture. One habit that pays for itself: post the method alongside the number. A figure without its method cannot be checked, and an unchecked figure is how this community accumulates folklore.

Moderator note: the sourcing question belongs in the vendor section and has been split out. Report rather than reply if it drifts again.