The International Fisher Effect (IFE) is an economic theory that describes the relationship between nominal interest rates, real interest rates, and exchange rates in different countries. The theory is based on the concept of purchasing power parity (PPP) and was developed by the economist Irving Fisher.

Key points about the International Fisher Effect (IFE) include:

1. **Theory**: The International Fisher Effect posits that changes in nominal interest rates between two countries are offset by changes in the exchange rate of their currencies, such that the real interest rates are equalized across countries. In other words, if the nominal interest rate in one country increases relative to another country, the currency of the first country is expected to depreciate in the foreign exchange market to maintain parity in real interest rates.

2. **Interest Rate Parity**: The IFE is closely related to interest rate parity, which states that the difference in nominal interest rates between two countries is equal to the difference in their expected rates of depreciation or appreciation of their currencies. Under interest rate parity, investors should not be able to profit from differences in interest rates between countries after accounting for exchange rate movements.

3. **Purchasing Power Parity (PPP)**: The IFE is based on the assumption of purchasing power parity, which suggests that in the absence of transaction costs and barriers to trade, the exchange rate between two currencies should adjust to equalize the prices of identical goods and services in different countries. Under PPP, changes in exchange rates reflect changes in relative price levels between countries.

4. **Implications for Investors**: The IFE has implications for international investors and financial markets. It suggests that investors should consider not only nominal interest rates but also expected changes in exchange rates when making investment decisions in different countries. If the IFE holds true, investors may need to adjust their portfolio allocations to account for currency risk and interest rate differentials.

5. **Empirical Evidence**: Empirical studies have provided mixed evidence on the validity of the International Fisher Effect. While some studies have found support for the relationship between nominal interest rates and exchange rates consistent with the IFE, others have observed deviations from the theory due to factors such as capital controls, market frictions, investor expectations, and central bank interventions in currency markets.

6. **Policy Implications**: The IFE has implications for monetary policy and exchange rate management. Central banks may take into account the expected impact of changes in domestic interest rates on exchange rates when formulating monetary policy decisions. Similarly, policymakers may intervene in currency markets to influence exchange rates and maintain stability in real interest rates.

Overall, the International Fisher Effect provides a theoretical framework for understanding the interplay between nominal interest rates, real interest rates, and exchange rates in an open economy. While the theory has limitations and may not hold true in all circumstances, it offers valuable insights into the dynamics of international financial markets and the behavior of investors and policymakers.