This paper evaluates the purchasing power parity (PPP) theory in a panel of Sub-Saharan African (SSA) countries. The study applies unit root tests that are based on exponential smooth transition autoregressive (ESTAR) models to account for nonlinearities and asymmetries in real exchange rate adjustment towards its equilibrium (mean) value. Nonlinearities and asymmetries are very relevant for these countries and are potentially due to transaction costs, trade barriers and other market frictions, and frequent official interventions in the foreign exchange market. Results indicate that once nonlinearities and asymmetries are taken into account there is more empirical support for the PPP theory in SSA.

This paper revisits the claim that flexible exchange rates facilitate external adjustments, in a panel of emerging market and developing economies. In contrast to previous studies which mainly use the exchange rate regime classification as a proxy for exchange rate flexibility, the present study estimates a measure of exchange rate flexibility that considers autoregressive conditional heteroskedasticity (ARCH) effects and possible asymmetric responses of the exchange rate to shocks. Generalized method of moments (GMM) estimators are employed to estimate the dynamic relationship between exchange rate flexibility and the speed of current account adjustment. The results suggest that more flexible exchange rates are associated with faster adjustment of current account imbalances, and when the possibility of an asymmetric response of exchange rate to shocks is taken into account, the estimated speed of adjustment is even higher.

This paper employs wavelets to examine the relationship between money, interest and output on a scale-by-scale basis using data for the US and Sweden during 1985-2017. First, series are decomposed into orthogonal timescale components using the discrete wavelet transform (DWT) together with the Daubechies least asymmetric wavelet filter, and then causality analysis (in the Granger sense) is performed at each scale of variations. The dynamics at the finest scale of one-year movements indicate that interest rate and real output respond to movements in the quantity of money. At horizons of four years and above, there is a feedback mechanism. This pattern is very similar in both countries at the mentioned scales and suggests that monetary disturbances have significant real effects and these effects last longer than is assumed in pure real-business cycle models. Further, a locally weighted regression analysis suggests that not only are the direction and strength of the relationship among these variables scale-dependent but also the shape of the relationship may change from one scale to another. This method suggests a negative relationship between money and the short-term interest rate, as predicted by the liquidity preference theory, at cycles of one to four-year periods. Overall, these findings highlight the relevance of timescale decomposition in macroeconomic analysis.