Yes, probably deletions. The rationale for "rewriting history", last time I asked Erik, is that if the pages got deleted they should arguably never have been created.

Andrew Gray, 17/03/2013 15:52:

On 17 March 2013 13:55, Jan Ainali wrote:

How come the historical statistics vary over time? Last month I looked at
the statistics for Swedish Wikipedia and it had 132 new Wikipedians in
December 2012 and 142 for November. When the January stats came now it says
it was 139 in December and 144 in November. How is that possible?

"New Wikipedians" counts people who have edited at least ten times
since registering an account; however, they don't have to make all ten
edits in that month.

http://stats.wikimedia.org/EN/TablesWikipediansNew.htm

So if someone registers in December and makes two edits, they won't
show up on that list; if they come back in January and make eight
more, then when the stats are recalculated they'll show up as a new
user for December.

In this case, you should file a bug, because they're supposed to show up as new users in January: <https://www.mediawiki.org/wiki/Analytics/Metric_definitions#Contributor> (disclaimer: I added that line myself).

Nemo

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