Correct. A zap given to a post from before December will not be counted in these. Unfortunately, I don't think I can publicly access the actual zap table, so I'm not able to see timing of zaps. Thus, the data just grabs posts and comments made in December and counts how many sats they had at the time of data extraction.

I suppose ~econ not making it to the top of the zaps is what flagged it for you?