Exhibit 11 WESTAMERICA BANCORPORATION Computation of Earnings Per Share on Common and Common Equivalent Shares and on Common Shares Assuming Full Dilution (In thousands, except per share data) For the three For the nine months ended months ended September 30, September 30, --------------------- ---------------------- 1997 1996 * 1997 1996 * ------- ------- -------- ------- Weighted average number of common shares outstanding 14,390 14,080 14,355 14,248 Add exercise of options reduced by the number of shares that could have been purchased with the proceeds from such exercise 279 270 255 269 ------- ------- ------- ------- Total 14,669 14,350 14,610 14,517 ======= ======= ======= ======= Net income $17,660 $11,903 $29,838 $34,371 Primary earnings per share $1.23 $0.85 $2.08 $2.41 ====== ====== ====== ====== Fully-diluted earnings per share $1.20 $0.83 $2.04 $2.37 ====== ====== ====== ====== * Restated on a historical basis to reflect the April 12, 1997, acquisition of ValliCorp Holdings, Inc. on a pooling-of-interests basis.