traveltech_sara said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Adding the part of the answer the thread has not reached. The useful move here is to separate what is established from what is widely repeated. Those two sets overlap less than the confident tone of most write-ups suggests, and the second set is where nearly all the disagreement on this board comes from.

One concrete data point for the thread. 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 would you tell the difference between that and the alternative explanation?

NicoleRaleigh said:

One practical note: write down what you did and when, before you need it.

I read this differently from NicoleRaleigh, on substance rather than tone. Pushing back on the consensus forming here. Consistency is not the same as correctness, and a board that agrees with itself quickly is usually agreeing with the first person who sounded certain.

NicoleRaleigh said:

One practical note: write down what you did and when, before you need it.

True, and it depends on a baseline nobody has stated. Without knowing where someone started, the same number can be an excellent result or a disappointing one.