Lewis (1988) proposes a multi-lateral approach to portfolio balance modelling where authorities could target the exchange rate by swapping the currency denomination of outside debt held by private investors while leaving the money supply unchanged. This is a kind of sterilised intervention in the foreign exchange market but it is achieved via a different, and probably a more convenient, means Cadsby (1987) considers a two-country portfolio balance model similar to the cases demonstrated in Section 3 of this chapter. The question of Walrasian stability is pondered, and conditions and assumptions under which stability is guaranteed or not guaranteed are reflected and derived. Empirical investigations have also been carried out in Lewis (1988). Bond data of the US, the UK, West Germany, Canada and Japan from January 1975 through to December 1981 are used in the study. Despite the attempts to use improved and more efficient empirical techniques, the results of the study indicate that estimates of the portfolio balance model remain plagued by imprecision, declares the author. He continues by offer ing that one possible explanation is that the model is not empirically valid and, in