Transactions in Contract for Difference (CFD) markets are increasing. However, because of the limited information and data, it is difficult to grasp the characteristics of the market as a whole. In Japanese CFD markets, the market maker system has been adopted. In market maker system, brokers called market makers act as intermediaries. Specifically, Market makers indicate both buy and sell quotes and guarantee execution on investors’ orders. Although market makers play an important role in providing liquidity to the market, there are few studies on their behaviors due to the limited data available.
The main source of profit for market makers is“ spread ”, the difference between the limit prices of both buy and sell orders to the market executed in equal units. On the other hand, the position generated when only one side of the orders is executed is exposed to the risk of price change of the underlying asset. Such a position held by a market maker due to his or her bias in buying and selling is called“ inventory ”. Market makers sometimes manage their inventory by hedging, which is referred to as counter-orders to the underlying asset market. They can reduce inventory more quickly and reliably by hedging than adjustment of the quotes, but are usually forced to bear hedging cost because they are price taker in undelying asset market. Therefore, market makers need to manage the spread profit, inventory risk, and hedging costs.
In this study, we reproduce CFD market on an artificial market simulation. We derive a Markov decision process (MDP) of CFD market makers over a discretized time horizon and train the CFD market maker, a deep reinforcement learning agent, using an artificial market simulation and analyze the details of the strategy using the proposed method. The proposed method is based on the design of reward function that contains the factors market makers should consider: spread, hedging costs, and inventory, and it simultaneously achieves risk management and profit maximization while providing liquidity as a market maker. Our model outperformed the baselines including the traditional market making strategy without hedging and deep reinforcement learning model that uses profit and loss (PnL) as a reward function. Also, our model was found to use two different risk management tools, limit price adjustment and hedging, based on the amount of inventory, market trend and volatility, and expected hedging cost.
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