Market Freeze and Recovery: Trading Dynamics under Optimal Intervention by a Market-Maker-of-Last-Resort

In the context of a search model of asset trading with adverse selection, we demonstrate that trading of a financial asset will cease, when its average quality drops sufficiently. A large player, however, can establish trading again, if he removes a sufficiently large quantity of bad assets which involves assuming losses. Most importantly, we show that such a player does not have to intervene immediately: a mere announcement today of intervening in the future can cause markets to function again. This announcement effect gives rise to a trade-off between the size and the timing of the intervention. The optimal policy balances the (social) costs of transfers against the costs of illiquid markets. If the former are small, it is optimal to ensure that markets function continuously. This is optimally achieved by intervening immediately, but at a minimum scale. When the costs of transfers increase, it is however optimal to delay the intervention and increase its size.