EXHIBIT 11 MARKWEST HYDROCARBON, INC. COMPUTATION OF EARNINGS PER COMMON SHARE (000s, except per share data) For the quarter ended March 31, 1999 -------------------------- Net income 111 Weighted average number of outstanding shares of common stock 8,478 Basic earnings per share $ 0.01 ========================== Net income 111 Weighted average number of outstanding shares of common stock 8,478 Dilutive stock options 3 -------------------------- 8,481 Earnings per share assuming dilution $ 0.01 ==========================