Each one, at different sizes and ages of a project.

I'm being unnecessarily sassy about it, but I subscribe to a software development lifecycle where writing as little code as possible (but no less) is a virtue.

If a project maintainer _merely_ maintains scope, plans release timelines, manages technical contributors, writes comms and documentation, enforces quality standards... that's plenty of software development.

Or from another perspective, a healthy project should still be viable if they lose core maintainers for whatever reason. If there's only one person who could possibly maintain part of the project that's a red flag.

Completely agree. The percentage depends a lot on both the age and scale of the project.

If a project has 100 active contributors, the mean contribution of new code will be 1% per contributor. How many of those are core? Maybe 10 or 20? So maybe there each writing 2-3% of new code and you have a decaying distribution? But that’s a moderately large project.

One of my projects started at 100% code written by me, but we did a release last year where none of the new code was written by me (it was all reviewed by me) and even the release was done by someone else, I just approved it. That’s a project with 2-3 moderately active contributors and a load of tiny drive-by contributors.

I'd like core maintainers to supply project direction and consistent purpose.

Wouldn't it depend on many factors *about * the project? There are A+ projects out there that are wholly on one person. And there are great projects out there that couldn't possibly be managed by less than a team numbering in the double-digits (like linux itself, or Python) and in those, a "core maintainer" could be much more PM or QA/Validation than coder.