Details about highly compensated individual testing?

[XTitan]

I've been reading 105(h)(5) and 1.105-11, and I just can't find any clear answers about who is "among the highest paid 25 percent of all employees" ?

Is it nothing more than looking at the number of employees as of the end of the plan year, ranking them by 415 comp, and calling the top 25% highly compensated individuals? Or, do you need to include the comp of any employee who received a reimbursement but may have left before the end of the plan year? Is it possible to make a determination who is top 25% in the middle of the plan year?

XTitan