I known that total merit sources have not changed, but one guy applied to be a merit source in Polish board.
[Polish section] Merit source application
Consequently, those topics he/she mentioned to apply got massive merits.
It is not only reasons of last week merit rises, but maybe one of partial or componential reasons.
I don't know Polish, but you can scrap data to see which boards have highest merit circulation last week.

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Additionally, this one: https://bitcointalk.org/index.php?topic=4315322.0
This is why in previous thread, I mentioned several merit source applications.