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, --------------- ------------------- 1999 1998 1999 1998 ---- ---- ---- ---- Earnings Applicable to Common Stock 10,151 $ 3,445 $ 33,557 $ 25,978 Debenture Interest Less Taxes 106 111 212 221 ------ -------- ------- ------- Net Income Available for Diluted Common Stock $ 10,257 $ 3,556 $ 33,769 $ 26,199 ======== ======== ======== ========= Average Common Shares Outstanding 24,946 24,444 24,915 23,673 Stock Options 16 41 17 43 Convertible Debentures 483 503 483 503 ------ -------- ------- ------- Diluted Common Shares 25,445 24,988 25,415 24,219 ====== ======== ======== ========= Diluted Earnings per Share $0.40 $0.14 $1.33 $1.08 of Common Stock ====== ======== ======== =========