Exhibit 11 WESTAMERICA BANCORPORATION Computation of Earnings Per Share on Common and Common Equivalent Shares and on Common Shares Assuming Full Dilution - ---------------------------------------------------------------------------- For the three months ended March 31, (In thousands, except per share data) 1999 1998 - ---------------------------------------------------------------------------- Weighted average number of common shares outstanding - basic 39,632 42,741 Add exercise of options reduced by the number of shares that could have been purchased with the proceeds of such exercise 640 818 - ---------------------------------------------------------------------------- Weighted average number of common shares outstanding - diluted 40,272 43,559 ============================================================================ Net income $18,405 $18,095 Basic earnings per share $0.46 $0.42 Diluted earnings per share $0.46 $0.42