CL should depend on how much you spend!
An adviser I used to work with taught me that an ideal CL should actually depend on how much you spend and NOT on your annual income.
To be specific: Total CL should be 10 – 15 times your total monthly spends.
This way, assuming that you always PIF every month, your total utilization never/rarely exceeds 10%, which is a good in respect to FICO credit score.