" The term bellwether refers to the practice of placing a bell around the neck of a castrated ram (a wether) leading his flock of sheep. While out of sight, the sound of the bell is a directive on the whereabouts of the flock. When earning season begins, the bellwether stock is that of the largest (typically industrial) companies who report their earnings. Analysts look to these reports as an indication of how subsequent reports will come in under or over expectations. "

― Coreen T. Sol , Practically Investing: Smart Investment Techniques Your Neighbour Doesn't Know