It might be zero for some people, but it's actually-- it is--the standard rate for people who have not negligible income is 15%.

对某些收益较少的人来说税率是零,但实际上...,对于大部分投资获利的人来说,标准税率是15%

耶鲁公开课 - 金融市场课程节选

If you have profit sharing in a firm or profit sharing in homework assignment, or any joint projects, you have to worry about too little effort being contributed because there's an externality.

如果你是一个公司的股东,或者和别人一起做作业及其他合作项目,你们需要注意到因为外部性,实际上每个人都付出了较少的努力

耶鲁公开课 - 博弈论课程节选