The fascinating thing to me is that author rewards dropped from 75% to 50% in August of 2019,

but I'm not sure if you can see that change in the posting trends. If it had any effect at all, it caused the decline to level off until the 2020 chaos.

Also, I have no idea what that big spike in posting is during late summer/fall of 2020. That doesn't seem to be linked to price at all.

I'll bet, the sharp downward spike in August/2019 of the posting graph from @o1eh (here) was when the blockchain was impaired for ~2 days between HF21 and HF22.

$ ./list_hardfork_dates.sh
0.0.0 "2016-03-24T16:00:00"
0.1.0 "2016-04-25T17:30:00"
0.2.0 "2016-04-26T18:00:00"
0.3.0 "2016-04-27T13:00:00"
0.4.0 "2016-04-30T15:00:00"
0.5.0 "2016-05-31T17:00:00"
0.6.0 "2016-06-30T14:00:00"
0.7.0 "2016-07-04T00:00:00"
0.8.0 "2016-07-04T01:00:00"
0.9.0 "2016-07-14T00:00:00"
0.10.0 "2016-07-15T12:00:00"
0.11.0 "2016-07-17T15:00:00"
0.12.0 "2016-07-26T15:00:00"
0.13.0 "2016-08-15T14:00:00"
0.14.0 "2016-09-20T15:00:00"
0.15.0 "2016-11-08T16:00:00"
0.16.0 "2016-12-06T16:00:00"
0.17.0 "2017-03-30T15:00:00"
0.18.0 "2017-03-30T15:00:00"
0.19.0 "2017-06-20T15:00:00"
0.20.0 "2018-09-25T15:00:00"
0.21.0 "2019-08-27T15:00:00"
0.22.0 "2019-08-29T15:00:00"
0.23.0 "2020-05-20T14:00:00"