EXHIBIT 11 YANKEE ENERGY SYSTEM, INC. AND SUBSIDIARIES Basic and Diluted Earnings Per Share Computation For the Years Ended September 30 -------------------------------- 1998 1997 1996 ---- ---- ---- (In thousands,except share data) Net Income 10,883 16,957 21,919 ----------- ----------- ----------- Weighted Average Common Shares Outstanding Basic 10,495,806 10,451,165 10,435,231 ----------- ----------- ----------- Stock Options 5,605 2,153 2,230 ----------- ----------- ----------- Diluted 10,501,411 10,453,318 10,437,461 ----------- ----------- ----------- Basic Earnings Per Share $ 1.04 $ 1.62 $ 2.10 ----------- ----------- ----------- Diluted Earnings Per Share $ 1.04 $ 1.62 $ 2.10 ----------- ----------- -----------