That's a really tough question to which there is NO easy answer. I've resolved myself to awarding bonuses on an annual basis about two weeks before Christmas. Awarding bonuses on a "per-job" basis is always difficult because there is so much that goes on behind-the-scenes that a project manager might cover. Other employees might be fully aware of how "Employee 138" missed three days of work, yet the project was completed on-time.
By offering an across-the-board bonus, it might might not be very popular, but it tells all employees that regardless of the project(s) that they complete successfully, ALL of them must be done this way in order for there to be any extra money to share.
I know that the good employees probably lose out with this strategy, but at least it encourages the rest to put forth the effort. It also helps us weed out those who are not true team players. It's not about the project; it's about the company as a whole.
