Most of the foreign exchange intervention literature overlooks the influence of market uncertainty when evaluating effectiveness. In this paper we take a fresh new look at how this uncertainty amplifies exchange rate effects. Our contribution is twofold. We first posit a partial equilibrium model with frictions to illustrate that when uncertainty is low, intervention is less effective, for agents are willing to bet against the central bank. Conversely, when uncertainty is high, intervention faces a weaker countervailing force from speculators and arbitragers. Second, we empirically test for the incremental effects of flimsy exchange rate fundamentals by using a sharp policy discontinuity in the way the Central Bank of Colombia intervened in the FX market. Our results indicate that market uncertainty increases depreciation of domestic currency in approximately 2 percentage points (pp) following central bank purchases of foreign currency and extends its duration in up to 4 weeks. Additionally, these purchases have an incremental effect in curbing exchange rate volatility in close to 5 pp.
