# 国际宏观经济学 International Macroeconomics ECON60132T

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$$1+i_{t}=\left(1+i_{t}^{}\right) \frac{F_{t}}{S_{t}} .$$ When (1.2) is violated a riskless arbitrage profit opportunity is available and the market is not in equilibrium. For example, suppose there are no transactions costs, and you get the following 12-month eurocurrency, forward exchange rate and spot exchange rate quotations $$i_{t}=0.0678, \quad i_{t}^{}=0.0422, \quad F_{t}=0.9961, \quad S_{t}=1.0200 .$$

## ECON60132TCOURSE NOTES ：

It will be the case that $i_{a}>i_{b}, i_{a}^{}>i_{b}^{}, S_{a}>S_{b}$, and $F_{a}>F_{b}$. An arbitrage that shorts the dollar begins by borrowing a dollar at the gross rate $1+i_{a}$, selling the dollar for $1 / S_{a}$ pounds which are invested at the gross rate $1+i_{b}^{}$ and covered forward at the price $F_{b}$. The per dollar profit is $$\left(1+i_{b}^{}\right) \frac{F_{b}}{S_{a}}-\left(1+i_{a}\right) .$$
Using the analogous reasoning, it follows that the per pound profit that shorts the pound is
$$\left(1+i_{b}\right) \frac{S_{b}}{F_{a}}-\left(1+i_{a}^{*}\right) .$$