index of current marriage fertility

例句：

1. 1. The index of the stock market is closely watched by investors.
   投资者密切关注股市的指数。
2. 2. The index of happiness has been rising steadily since the pandemic began.
   自大流行开始以来，幸福指数一直在稳步上升。
3. 3. The index of unemployment in this region has dropped significantly since the government implemented a new policy.
   自从政府实施了一项新政策后，该地区的失业率大幅下降。