Equation #6 · Chapter 2

Legacy Friction Coefficient μ_leg

\mu_{leg} = \frac{Years\_Since\_Last\_Update}{Pages\_of\_Documentation}

Legacy Friction Coefficient

μ_leg · Ch 2

Years since last update ÷ pages of documentation. Obscure + terrifying = nobody will touch it.

Worked example — A claims-routing service nobody touches

Last meaningfully changed in 2016. Documented by a 40-page wiki page written by someone who left in 2019.

It came out at 0.23. Green — low friction, because the docs still cover it.

Now audit the wiki and find that 32 of those pages describe screens that no longer exist. Eight real pages: 1.1, mid friction — and that is your opening, not your problem. High friction means you get to be the only person who understands it.

Your turn — change one number

Years since last real update9

Pages of documentation40

Result0.23

Green. Low friction. Documented, touchable, boring — in the good way.