摘要：In this article we re-examine the mean-reverting property of the current account for the US, the UK, Canada and France. This is important because a current account that is not a stationary process implies that the external debts are unsustainable. The empirical results show that the current account-GDP ratios for the four countries are non-stationary processes based on the traditional unit root test. Bierens' non-linear unit root test results show that these current account-GDP ratios could exhibit mean stationarity, trend stationarity and non-linear trend stationarity once we account for a more general specification of the non-linear deterministic components based on a Chebishev polynomials approximation. One should, therefore, be cautious when concluding that the current account is sustainable or unsustainable based upon the traditional unit root test since it overlooks the non-linear property intrinsic in the data
