This graphic needs more context/metrics. Are these judgments made on past trends? Usage numbers? Something like how MacRumors buying guide averages out past release schedules to determine the next likely update:
I've always wondered...how do you go about discussing such things as recommendations/references in this situation? If you are one of the employee's only employers, you'll likely be one of his/her only references...
Do you talk about the situation? And how much of is it contingent on the circumstances of their leaving (obviously a reference would be out of the question if the firing was for severe misconduct)?
http://buyersguide.macrumors.com/