Ad valorem platform fees, indirect taxes, and efficient price discrimination
解释了亚马逊和Visa等平台为何主要采用从价费用（随交易价格比例增加），并说明从价销售税优于从量税的新理由，基于从价费用和税收能实现有效价格歧视。
This article explains why platforms such as Amazon and Visa rely predominantly on ad valorem fees, fees which increase proportionally with transaction prices. It also provides a new explanation for why ad valorem sales taxes are more desirable than specific taxes. The theory rests on the ability of ad valorem fees and taxes to achieve efficient price discrimination, given that the value of a transaction to buyers tends to vary proportionally with the cost of the good traded.