Dr.ObesityMed said:

International shipping tracking for cross-border ordering orders: my experience with customs in the US when ordering from overseas: Held at customs…

Pushing back on Dr.ObesityMed here. Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions. What is a personal-import allowance in one country is a controlled-import offence in another.

Adding the numbers, since they settle part of this. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

BenResearch_OR said:

Import rules are jurisdiction-specific and this board keeps giving US-shaped answers to non-US questions.

There is a second half to this that has not been said yet. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.

A narrower follow-up, since the general answer is now clear:

How would you tell the difference between that and the alternative explanation?

Reporting back.

Update, and it is the boring outcome: nothing was wrong. The measurement I was reading had moved less than its own week-to-week variation, which somebody said upthread and I did not believe.