Multi-agent reinforcement learning for market microstructure statistical inference

Quantitative finance has had a long tradition of a bottom-up approach to complex systems inference via multi-agent systems (MAS). These statistical tools are based on modelling agents, which trade via a centralised order book to emulate complex and diverse market phenomena. Nevertheless, the issue of agent learning in MAS, which is crucial to price formation and hence to all market activity, has not yet fully benefited from the recent progress of artificial intelligence, and namely reinforcement learning. In order to address this, we present here a next-generation MAS stock market simulator, in which each agent learns to trade autonomously via reinforcement learning. We calibrate it to real market data from the London Stock Exchange over the years 2007 to 2018, and use it to highlight the beneficial impact of agent suboptimal learning on market stability.