Settlement Encouragement and Fairness Act - Defines "prevailing party" for any Act of Congress, any agency ruling, regulation, or interpretation, or any judicial or administrative rule that provides for the recovery of attorney's fees, to include, in addition to a party who substantially prevails through a judicial or administrative judgement or order or an enforceable written agreement, a party whose pursuit of a non-frivolous claim or defense was a catalyst for a voluntary or unilateral change in position by the opposing party that provides any significant part of the relief sought.