两头小， 中间大

两头小， 中间大 [liǎng tóu xiǎo zhōng jiān dà]

1. ■ a few at each extreme and many in between; small at both ends and big in the middle:

“我看什么地方都是两头小， 中间大。” “I believe it is true everywhere that people at the two poles are few while those in the middle are many.”