Wavelet-Based Analysis of the Comovement Between Exchange Rate and Stock Returns in SACU Countries

The Southern African Customs Union is the oldest customs union in the world and the member states form a currency union with the South African Rand being the regional currency anchor. Therefore, currency movements amongst SACU members are dependent on developments of the Rand which, in turn, can affect stock market development in the region. We examine the time-frequency relationship between exchange rates and stock market returns in SACU countries using continuous wavelet transforms. Our empirical analysis is two-staged. Firstly, we employ wavelet power spectrum to examine the time-frequency properties of the individual series. Secondly, we use wavelet coherence analysis and phase dynamics to examine the synchronization between the variables in a time-frequency space. Our findings show stronger (weaker) exchange rate-stock returns relations during periods of higher (lower) inflation whereas we observe a stronger (weaker) relationship during periods of lower interest rate environment. Moreover, we find more significant long-run relationships for countries with more independent monetary policy (South Africa and Botswana) whereas these relations are more prominent over the short-run for countries with pegged exchange rates (Eswatini and Namibia). We also observe that periods of oil and currency shocks impact the exchange rate-stock returns relationship in SACU countries with pegged exchange rates (Eswatini and Namibia). Our findings bear important implications for different stakeholders. For instance, this study has implications for exchange rate policy as it addresses whether the exchange rate can be used to improve market performance or whether exchange rate developments spill over into the stock market. Furthermore, corporate managers and stock market participants would be interested in our findings as it identifies periods of market inefficiency when exchange rates can be used to beat the stock market.