Bitergia.io shows a slow but steady decline over most metrics of the technical community, starting 2013-ish:
|Commit authors||Changeset owners||Email authors|
This is not a new insight but apparently T103292: Check whether it is true that we have lost 40% of (Git) code contributors in the past 12 months did not result in any action. It is also not very reliable (bitergia does not filter out upstream repos, does not differentiate between new commits and cherry-picks etc), but even so the speed of the decline and its consistency over most metrics should be cause for alarm. When similar but much less rapid decline was noticed in editors and readers, it led to major organization-level efforts to address it. It feels like the technical community version of the decline does not get the attention it would deserve.