I should have added that it only applies to some companies. Finance is a special case because if a lot of traders leave at the same time, the ones who stay wil

I should have added that it only applies to some companies. Finance is a special case because if a lot of traders leave at the same time, the ones who stay will have more capital to play with. Consulting/contracting/auditing firms are very different: they are committed to specific projects for specific clients and have already negotiated the fees. So it's real trouble if employees leave all at once--you cannot simply move their projects/clients to the employees who stay (because it creates even more overworked employees who will leave asap after the next bonus). Also these projects may be much shorter than a year, some audit works are done within one-two weeks. If the firm negotiated a 2 weeks project for $XX fees and the employees on that project manage to finish the project for far less resources, the firm knows that they made a huge profit on that project. The firm may give these employees an instant bonus so that the employees are incentivised to reiterate the performance for the next project.