As every quarter I’ve updated the contributor statistics in the OSM wiki. The most notable effect is the drop off in new contributors in the 2nd half of 2021, which can at least partly be attributed to the demise of maps.me as a source of new mappers.
This is more obvious when you consider just the new users from this source
Note that the numbers include new users using organic maps, but even that doesn’t change the trend.
See my diary posts from 2020, 2018 and 2017 for more on the topic.