bellwether

noun

1. The leading sheep of a flock, having a bell hung round its neck.

   “Several old ladies forthwith proclaimed their intention of following him; but, as one or two of them were deaf, and another had been threatened with an attack of that mild, but obstinate complaint, dementia senilis, many thought it was not so much the force of his arguments as a kind of tendency to jump as the bellwether jumps, well known in flocks not included in the Christian fold.”

2. (figuratively)Anything that indicates future trends.

   “Mortgage delinquencies often act as a bellwether for a forthcoming recession.”

   “At Hampton Court the little flocks of visitors are not provided with an official bellwether, but are left to browse at discretion upon the local antiquities.”

   “I suspect that, after all,[…]—that all this has been known, perhaps for ages, to certain ones upon this earth, a cult or order, members of which function like bellwethers to the rest of us, or as superior slaves or overseers, directing us in accordance with instructions received—from Somewhere else—in our mysterious usefulness.”

   “In December, after everyone had weighed in, Nature, a bellwether of mainstream scientific thought for more than a century, cautiously supported a future of automated scientific scrutiny in an editorial that addressed the Statcheck controversy without explicitly naming it.”

   “A bellwether election in Germany’s most populous state has shown a further eroding of support for populist parties on the far ends of the political spectrum, thrown up questions over the pulling power of the chancellor, Olaf Scholz, and entrenched the growing authority of the Greens.”

3. (figuratively)A stock or bond that is widely believed to be an indicator of the overall market's condition.

   “One of my favorite sentiment indicators is bellwether stocks — key stocks that are leaders in their fields. When investors buy or sell these shares, it's usually a good sign of confidence or the lack of it in that sector of the market and sometimes even the economy.”