We model endogenous trading and liquidity provision at a decentralized exchange (DEX) and demonstrate that increasing DEX trading fees can increase DEX trading volume. DEXs employ a mechanical pricing rule whereby price impacts decrease with inventory that DEXs acquire by offering fee revenues to investors. Consequently, higher DEX fees can incentivize higher inventory, thereby reducing price impacts. Moreover, the reduction of price impact can offset the increase in fees so that the marginal cost of DEX trading declines despite charging a higher trading fee. In turn, lower DEX marginal trading costs lead to an increase in DEX trading volume. This paper was accepted by Agostino Capponi, finance.
Hasbrouck et al. (Tue,) studied this question.