EVALUATING the past performance of companies in which we have an investment is a daunting task. Decisions often are based on hunches, the advice of stockbrokers, and the media. Sometimes a herd mentality drives investment decisions.

EVALUATING the past performance of companies in which we have an investment is a daunting task. Decisions often are based on hunches, the advice of stockbrokers, and the media. Sometimes a herd mentality drives investment decisions.