An actuation system for variable stator vanes pivotally mounted in a casing includes a plurality of levers joined to the respective vanes. An actuation ring coaxially surrounds the casing adjacent to the levers. A plurality of circumferentially spaced apart ring guides are joined to the casing for guiding circumferential rotation of the ring. Respective slip joints are provided between each of the levers and the actuation ring for varying pivot length of the levers as the ring is rotated for effecting nonlinear vane actuation.