While the broader market gained around 27% in the last year, Westamerica Bancorporation shareholders lost 7.1% (even including dividends). However, keep in mind that even the best stocks will sometimes underperform the market over a twelve month period. Unfortunately, last year's performance may indicate unresolved challenges, given that it was worse than the annualised loss of 1.7% over the last half decade. We realise that Baron Rothschild has said investors should "buy when there is blood on the streets", but we caution that investors should first be sure they are buying a high quality business. I find it very interesting to look at share price over the long term as a proxy for business performance. But to truly gain insight, we need to consider other information, too. For instance, we've identified 2 warning signs for Westamerica Bancorporation (1 makes us a bit uncomfortable) that you should be aware of.