Because the tunnel economy is clandestine, it's difficult to estimate just how much money is being made.

VOA: standard.2010.06.17

The investment rate is telling you how much money you're really making on an annualized basis, so it's very simple.

投资收益率反映了基于一年来看,你实际赚了多少钱,非常简单

耶鲁公开课 - 金融市场课程节选