EXHIBIT 11 NORTHWEST NATURAL GAS COMPANY Statement re: Computation of Per Share Earnings (Thousands, except per share amounts) (Unaudited) Three Months Ended Six Months Ended June 30, June 30, ------------------ ------------------ 1998 1997 1998 1997 ---- ---- ---- ---- Earnings Applicable to Common Stock $ 3,445 $ 1,694 $25,978 $25,774 Debenture Interest Less Taxes 111 117 221 234 ------- ------- ------- ------- Net Income Available for Diluted Common Stock $ 3,556 $ 1,811 $26,199 $26,008 ======= ======= ======= ======= Average Common Shares Outstanding 24,444 22,661 23,673 22,625 Stock Options 41 49 43 49 Convertible Debentures 503 533 503 533 ------- ------- ------- ------- Diluted Common Shares 24,988 23,243 24,219 23,207 ======= ======= ======= ======= Diluted Earnings per Share $0.14 $0.07 $1.08 $1.12 of Common Stock ===== ===== ===== =====