If you describe something as a bellwether, you mean that it is an indication of the way a situation is changing.
例句
For decades the company was the bellwether of the British economy...几十年来,这家公司一直是英国经济的晴雨表。IBM is considered the bellwether stock on Wall Street.国际商用机器公司的股票行情被视为华尔街股市的风向标。
英英词典释义
Noun
1. someone who assumes leadership of a movement or activity