The fundamental relationship of saving to investment, the fiscal balance, and the trade balance is S = I + (G − T) + (X − M), or (S − I) = (G − T) + (X − M). This relationship can be solved for the fiscal balance, (G − T) = (S − I) − (X − M), or for the trade balance, (X − M) = (S − I) − (G − T).
