bellwether

noun3

1. •
   The leading sheep of a flock, having a bell hung round its neck.
2. •
   (figurative) Anything that indicates future trends.

   • Mortgage delinquencies often act as a bellwether for a forthcoming recession.
3. •
   (figurative) A stock whose price performance is treated as an indicator of the likely direction of a broader market, sector, or industry.