China’s Mundell-Fleming Trilemma
The following is an excerpt from our weekly Market Brief. If you’re interested in learning more about Market Briefs and the Macro Ops Hub, click here.
You’re probably familiar with the story of how Soros and Druckenmiller “broke the Bank of England” in 92’.
The two bet against the pound believing that it couldn’t maintain its peg to the Deutsche Mark in the European Exchange Rate Mechanism (ERM). They were right. The Bank of England was forced to stop defending the peg and the pound plummeted. The Quantum Fund (Soros and Druckenmiller) netted over a billion dollars over the course of a few days. The rest is history.
It was an amazing trade. It had all the markings of a “perfect setup”; the kind that only come around once every decade or so. It was extremely asymmetric in that the risk was clearly defined by the upper-band of the ERM peg. And if the lower bound broke, like they expected, they knew the pound would collapse due to all the investors on the wrong side forced to liquidate.
It was also a fundamentally compelling trade. The thesis was based on an economic law derived from the Mundell-Fleming model. It states that in a world of high capital mobility, a central bank can target the exchange rate or the interest rate but not both. This economic reality is also known as the policy trilemma. Here’s the following explanation from The Economist:
The policy trilemma, also known as the impossible or inconsistent trinity, says a country must choose between free capital mobility, exchange-rate management and monetary autonomy. Only two of the three are possible. A country that wants to fix the value of its currency and have an interest-rate policy that is free from outside influence cannot allow capital to flow freely across its borders. If the exchange rate is fixed but the country is open to cross-border capital flows, it cannot have an independent monetary policy. And if a country chooses free capital mobility and wants monetary autonomy, it has to allow its currency to float.
To understand the trilemma, imagine a country that fixes its exchange rate against the US dollar and is also open to foreign capital. If its central bank sets interest rates above those set by the Federal Reserve, foreign capital in search of higher returns would flood in. These inflows would raise demand for the local currency; eventually the peg with the dollar would break. If interest rates are kept below those in America, capital would leave the country and the currency would fall.
Where barriers to capital flow are undesirable or futile, the trilemma boils down to a choice: between a floating exchange rate and control of monetary policy; or a fixed exchange rate and monetary bondage.
