Exhibit 11 - COMPUTATION OF PER SHARE EARNINGS (Thousands of dollars, except per share data) Twelve Months Ended December 31 1996 1995 1994 PRIMARY -------------------------------------------- Average shares outstanding 31,388,066 31,194,368 30,949,625 Net effect of stock options - based on the treasury stock method using average market price (1) (1) (1) -------------------------------------------- 31,388,066 31,194,368 30,949,625 Net income (loss) $138,937 $112,350 $68,464 Per-share amount $4.43 $3.60 $2.21 ===== ===== ===== FULLY DILUTED Average shares outstanding 31,388,066 31,194,368 30,949,625 Net effect of dilutive stock options - based on the treasury stock method using the year-end market price if higher than exercise price 366,785 300,637 152,471 -------------------------------------------- 31,754,851 31,495,005 31,102,096 Net income (loss) $138,937 $112,350 $68,464 Per-share amount $4.38 $3.57 $2.20 ===== ===== ===== (1) Incremental number of shares excluded from calculation since they do not have a dilutive effect.