index number of prices of trade conducted at rural fairs

例句：

1. 1. The index of the stock market is closely monitored by investors.
   投资者密切关注股市的指数。
2. 2. The index of the economy has been on a steady rise since the beginning of the year.
   自年初以来，经济指数一直稳步上升。
3. 3. The index of happiness is calculated based on surveys of people's lives.
   幸福指数是根据人们对生活调查的结果来计算的。