I love this question because I have the PERFECT solution. It's called Slicing Pie
and it's a formula for determining a perfectly fair equity split for any bootstrapped company no matter what changes.
The concept is simple: a person's % share of the equity should always be equal to that person's % share of the risk.
Risk is equal to the fair market value
of the contributions made by each participant. Contributions include money, time, ideas, relationships, supplies, equipment or anything else. Everything
has a fair market value.
Slicing Pie normalizes the fair market value of cash contributions and non-cash contributions (like time) by converting to a fictional unit called a "Slice"
So, at any given time, a person's share is equal to their slices divided by all the slices. It always stays perfectly fair!
Not only does it allow you to calculate a perfect split, but also it determines the fair buyout price, if any, when someone leaves. Slicing Pie is great, and it's used all over the world
I've written several books on this topic and you may have one if you contact me through SlicingPie.com