總體經濟參數與政策搭配問題

Macroeconomic Parameters and the Assignment Problem

鑑於CavesandJones（1973）探討政府應如何運用匯率政策與財政政策來追求全面均衡的目標時，僅以內部均衡線與外部均衡線的相對斜率做為抉擇政策搭配的依據，Chen（1977）乃進一步闡明內部均衡線和外部均衡線的斜率孰大孰小端視邊際進口傾向是否小於1／2而定。準此，邊際進口傾向是否高於1/2，遂成為當局決定政策搭配方式的準則。本文修訂Chen（1977）隱含經濟體系始終處於充分就業的頑強設定，考量所得也會影響貿易收支後發現：邊際進口傾向與邊際儲蓄傾向的相對大小，才是政府選擇政策搭配的決定因素。具言之，若邊際進口傾向高（低）於邊際儲蓄傾向，則應以匯率政策維持內（外）部均衡，而以財政政策維持外（內）部均衡；相反的搭配會導致經濟體系的動態不安定。 Caves and Jones (1973) employ the Swan diagram to illustrate the assignment problem and suggest that the slope of the external-balance schedule being flatter than the internal-balance schedule implies higher relative effectiveness of exchange-rate (government expenditure) changes for securing an external (internal) balance. Chen (1977) further demonstrates that Caves and Jones' proposition is valid if and only if the size of the marginal propensity to import falls short of one half. This clear result of Chen (1977) comes from the robust assumption that the output is fixed at the full-employment level. This present research assumes that, unless the economy is lying on the internalbalance schedule, the output is capable of influencing the trade balance. We therefore show that the relative magnitude between the marginal propensity to import and the marginal propensity to save is crucial in determining the policy assignment. More specifically, if the size of the marginal propensity to import is smaller (larger) than the size of the marginal propensity to save, then an exchange-rate policy should be set up to secure the external (internal) balance and a proper fiscal policy should be executed to secure the internal (external) balance.