EXHIBIT 11 NORTHWEST NATURAL GAS COMPANY Statement re: Computation of Per Share Earnings (Thousands, except per share amounts) (Unaudited) Three Months Ended Nine Months Ended September 30, September 30, --------------------- ----------------- 1998 1997 1998 1997 -------- -------- ------- ------- Earnings Applicable to Common Stock $ (6,558) $ (3,101) $19,420 $22,673 Debenture Interest Less Taxes 110 115 330 345 -------- -------- ------- ------- Net Income Available for Diluted Common Stock (6,448) $(2,986) $19,750 $23,018 ========= ======= ======= ======= Average Common Shares Outstanding 24,763 22,734 24,037 22,662 Stock Options 36 45 40 38 Convertible Debentures 500 522 500 522 -------- -------- ------- ------- Diluted Common Shares 25,299 23,301 24,577 23,222 ======== ======== ======= ======= Diluted Earnings per Share of Common Stock $(0.26) $(0.14) $0.80 $0.99 ======== ======== ======= =======