20% of gross is a good KPI incentive.
In my case, I get a 13th cheque and then also a KPI incentive equal to 15% of my annual gross. In that you can score between 80% and 120% of the individual targets set. There are roughly 8 individual KPI's ranging from very high level financial results on the one end of the scale, to low level 'easy-to-achieve-and-managible' ones.
What is nice about working on %'s, the percentage of your target is debated in another forum altogether. The negotiations move away from the money aspect, and is more focused on the KPI's and therefore more focused on what needs to be done. Another thing that I must say our company did well, was to implement KPI's which are cross functional, ie. all employees being measured on efficiencies as well as working capital. In this situation when you make a decision, you need to weigh up the options and make a call which is best for the company, and not necessarily for your function.