claudia_zurich said:

It is worth asking what the claim would look like if it were false.

Adding a me-too, because a thread of one person's experience is not much use. Posting only so the count is not one.

claudia_zurich said:

It is worth asking what the claim would look like if it were false.

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.

One concrete data point for the thread. 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.

Following on from claudia_zurich — and this may be the naive question:

What did you change at the same time, and can you separate the two now?

anders_CPH said:

One habit that pays for itself: post the method alongside the number.

I do not accept the framing. The question has been narrowed to the version that has a tidy answer, and the part that was dropped is the part the OP actually asked about.

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