Does maker-taker limit order subsidy improve market outcomes? Quasi-natural experimental evidence

Abstract

We provide a new theory of exchange access fees that explains why fees relatively reduce the probability of execution and increase the limit order queue length on “maker-taker” platforms. Nonetheless, the limit order subsidy greatly improves market depth, together with market efficiency and trading volume. Moreover, fee structures never “wash out” regardless of the minimum tick. The regulatory requirement that trading and order flow depend only on raw (nominal) spreads and prices underpins the multi-billion-dollar subsidy to limit orders. So long as a platform remains competitive, elimination of the fee structure does not alter the raw spread, but it does lower the cum fee spread. We test these implications with a unilateral maker-taker fee/rebate reduction using NASDAQ's “quasi-natural” $1.9 trillion experiment to find support for our theory.