Market Making with Model Uncertainty

Pari-mutuel markets are trading platforms through which the common market maker simultaneously clears multiple contingent claims markets. This market has several distinctive properties that began attracting the attention of the financial industry in the 2000s. For example, the platform aggregates liquidity from the individual contingent claims market into the common pool while shielding the market maker from potential financial loss. The contribution of this paper is two-fold. First, we provide a new economic interpretation of the market-clearing strategy of a pari-mutuel market that is well known in the literature. The pari-mutuel auctioneer is shown to be equivalent to the market maker with extreme ambiguity aversion for the future contingent event. Second, based on this theoretical understanding, we present a new market-clearing algorithm called the Knightian Pari-mutuel Mechanism (KPM). The KPM retains many interesting properties of pari-mutuel markets while explicitly controlling for the market maker's ambiguity aversion. In addition, the KPM is computationally efficient in that it is solvable in polynomial time.