The Advantage to Hiding One's Hand: Speculation and Central Bank Intervention in the Foreign Exchange Market

Using a portfolio balance model of exchange rate determination, this paper develops a theoretical explanation of why central banks do not make precise announcements of their exchange rate targets. In foreign exchange markets, where it is common knowledge that the central bank intervenes to stabilize the spot exchange rate around some target level, foreign exchange traders can exploit this fact to earn speculative profits from the central bank: this may cause the bank's reserves to fall to dangerous levels. We show that if the central bank is imprecise about its exchange rate targeting, it can use this informational advantage not only to reduce its reserve losses, but also to extract all relevant `fundamental' information from the traders. The imprecision, however, cannot be too large. There exist circumstances where the central bank finds it advantageous to reduce the market's ex ante uncertainty about the exchange rate target.