Stun Threshold Calc

Ive read that stun threshold default is % of life.

- Running Invoker Monk with CI and standard EV/ES Chest for the spirit ascendancy, therefore a node such as Asceticism would be beneficial to me I guess.

- Running a Pathfinder Ranger with CI and Ghostwrithe. Ghostwrithe Life to Energy shield is calculated prior to CI dropping to 1 - Does stun threshold calc from life before CI drops it to 1?

We know Asceticism is 30% of ES to stun threshold. Do we know the stun threshold value based on life?