Did the number of learners increase or decrease in 2016?
I would like to know based on your own personal experience, in addition to any official data that you know of.
Definitely grown with Duolingo for En>Eo. After Espana>Eo the growth is gone to +0.7 million/year (projected on current trend). Portuguese (keen learners) is hatching @ 7%.
My Duolingo EN>EO cumulative growth snapshots since Sep'16:
+930/day on 11Nov,
+1100/day on 14Dec,
+1200/day on 14Jan...
+1350/day current.
Espana>EO (some in both EN/ES>EO) +747/day
That's ~>42.2% increase of base speakers (EN+50%ES)/2mn.
Not including other sources.
Once again I'm reminded of my saying Esperanto Wasn't Born Yesterday™. Esperanto has a 130 year history and is not going to succeed or fail based on what happened in 2016. Ultimately we run into the same problems when we try to define how many speakers there are. What is a learner and how do we count them?
Your request for "official" data is a little odd, since there is no official source for data. It's not clear what "unofficial data" would be.
I recall that the Duolingo Esperanto course continues to grow with linear growth.
My personal experience is that I'm getting a lot more requests for help with Esperanto than I did 3 or 5 years ago -- but for sure that's because I'm out there more than I used to be. (I teach on italki, do translations by request, that sort of thing.)