Case 1, Total Compensation. Amazon does "total comp", which is your base plus RSUs. Suppose your grants were rather large, or "timed" at a downswing for AMZN. Your current vesting schedule for 2016 could exceed the planned target & salary band. I find no base adjustment whatsoever mildly surprising. But I would not be shocked.
Case 2, performance based compensation. As amzn-tway8 also mentioned your yearly compensation at amazon is related to your annual performance review. Read and understand the definitions of "Performance Rating" and "Leadership." Your manager will have discussed this with you in your annual review. Average and exceptional performance reviews will yield relevant compensation adjustments. Individuals with a very low performance review can expect a low, or possibly no, increase.