A model of market making with heterogeneous speculators

I introduce an optimizing monopolistic market maker in an otherwise standard setting à la Brock and Hommes (J Econ Dyn Control 22(8–9):1235–1274, 1998) (BH98). The market maker sets the price of a zero-yielding asset taking advantage of her knowledge of speculators’ demand, manages her inventory of the asset and eventually earns profits from trading. The resulting dynamic behavior is qualitatively identical to the one described in BH98, showing that the results of the latter are independent from the institutional framework of the market. At the same time, I show that the market maker has conflicting effects. She acts as a stabilizer when she allows for market imbalances, while she acts as a destabilizer when she manages aggressively her inventories and when she trades, especially if she acts as fundamentalist or if she is a strong extrapolator. Indeed the more stable institutional framework is one in which the market makers are inventory neutral and doesn’t trade but, even in this case, the typical complex behavior of BH98 occurs.