圣路易斯华盛顿大学的心理学家莱昂纳德和乔尔·迈尔森发现，给小费者人是否慷慨可能会受到帐单金额的影响。通过汇总服务员、出租车司机和发型师收到的近1000份小费的数据，他们发现这三个领域中小费的比例都随着顾客帐单金额的上升而下降。
In fact, tip percentages appear to plateau when bills topped 0 and a bill for 0 garnered the worker no bigger percentage tip than a bill for 0.

当帐单超过100美元后，小费的比例变化不明显。一笔200美元的消费对于服务员来说获得小费的比例并不比100美元的消费高。
Why? Green has his theories, including one he attributes to an old Woody Allen saying: "Eighty percent of success in life is showing up."

这是为什么呢？格林有他自己的理论，其中的一条他总结为伍迪·艾伦的名言：“生活中80%的成功是自我表现。”
"That's also a point of tipping," Green says. "You have to give a little extra to the cab driver for being there to pick you up and something to the waiter for being there to serve you. If they weren't there you'd never get any service. So I think part of the idea of a tip is for just being there."
   
格林说：“这一点对于给小费来说也很重要。对于接你的出租车司机和为你服务的服务员，你不得不给一点额外的小费。如果他们不存在，你就得不到任何服务，所以我认为给小费一部分是因为他们的存在。”
Green explains since everyone would earn the "just being there" tip, it's inevitable that portion would make up a larger percentage of smaller bills.
    
格林解释说，既然每个人都会获得“因为存在”的那部分小费，所以小费在较小金额的消费中必然占较大的比例。