The superscripts ‘+’ and ‘−’ indicate positive and negative partial sums, respectively. Δ is the first difference operator. β⁺and β^- are the estimated asymmetric long-term coefficients associated with positive and negative changes, respectively. t_BDM and F_PSS are t-statistic and F-statistic, respectively, for testing the null hypothesis of no nonlinear long-term relationships in the NARDL model. W_LR and W_SR are Wald statistics, for testing long-term and short-term asymmetric effects, respectively. Values in brackets {} are F-statistic. *, ** and *** represent significance levels at 10, 5 and 1%, respectively