A neuromodulation system and method of providing sub-threshold therapy to a patient. An anodic perception threshold of super-threshold electrical energy and a cathodic perception threshold of super-threshold electrical energy are determined for a plurality of electrode sets. A ratio between the anodic perception threshold and the cathodic perception threshold is calculated for each of the electrode sets. An effective electrode set is selected based on the ratio between the anodic perception threshold and the cathodic perception threshold,
