This excerpt taken from the ERES DEF 14A filed Mar 22, 2007.
Performance Shares are awards that will result in a payment to a participant only if performance goals established by the Compensation Committee are achieved or the awards otherwise vest. The Compensation Committee will establish performance goals in its discretion, which, depending on the extent to which they are met, will determine the number and/or the value of performance shares to be paid out to participants. The performance goals may be based upon the achievement of Company, business unit or individual goals (including solely continued service), or other basis determined by the Compensation Committee. Payment for performance shares shall be made in shares of our Common Stock with equivalent value, as determined by the Compensation Committee. Performance shares will have an initial value equal to the fair market value of our Common Stock on the grant date. The Compensation Committee also determines the number of performance shares granted to any participant and the performance period with respect to each award. Each performance share is evidenced by an award letter, and is subject to the terms and conditions determined by the Compensation Committee. The Compensation Committee shall have the discretion to determine the extent, if any, to which a participant is entitled to receive any performance shares if the participants service terminates prior to the expiration of the applicable performance period.