Sudden Stops and Optimal Foreign Exchange Intervention

This paper shows how foreign exchange intervention can be used to avoid a sudden stop in capital flows in a small open emerging market economy. The model is based around the concept of an under-borrowing equilibrium defined by Schmitt-Grohe and Uribe (2020). With a low elasticity of substitution between traded and non-traded goods, real exchange rate depreciation may generate a precipitous drop in aggregate demand and a tightening of borrowing constraints, leading to an equilibrium with an inefficiently low level of borrowing. The central bank can preempt this deleveraging cycle through foreign exchange intervention. Intervention is effective due to frictions in private international financial intermediation. Reserve accumulation has ex ante benefits by reducing the risk of a sudden stop, while intervention has ex-post benefits by limiting inefficient deleveraging. But intervention itself faces constraints. When the central bank's stock of reserves is low, even foreign exchange intervention cannot prevent a sudden stop.