International Finance Theory and Policy
by Steven M. Suranovic

Finance 40-12

# Integrating the Money Market and the Foreign Exchange Market

In this section we will integrate the money market with the foreign exchange market to demonstrate the interactions that exist between the two. First, a review.

In the money market the endogenous variable is the interest rate (i\$). This is the variable that is determined in equilibrium in the model. The exogenous variables are the money supply (MS), the price level (P\$) and the level of real GDP (Y). These variables are determined outside the money market and treated as known values. Their values determine the supply and demand for money and affect the equilibrium value of the interest rate.

In the foreign exchange market (FOREX) the endogenous variable is the exchange rate, E\$/£. The exogenous variables are the domestic interest rate (i\$), the foreign interest rate (i£) and the expected exchange rate Ee\$/£. Their values determine the domestic and foreign rates of return and affect the equilibrium value of the exchange rate.

The linkage between the two markets arises because the domestic interest rate is the endogenous variable in the money market and an exogenous variable in the FOREX market. Thus, when considering the FOREX, when we say the interest rate is determined outside of the FOREX market, we know where it is determined: it is determined in the US money market as the interest rate that satisfies real supply and demand for money.

Linking the Diagrams

We can keep track of the interactions between these two markets using a simple graphical technique. We begin with the money market diagram as developed in Section 40-7. The trick is to rotate the diagram 90° in a clockwise direction. The adjoining diagram shows the beginning of the rotation pivoted around the origin at 0.

When rotated the full 90° it will be positioned as shown in the second diagram. The most important thing to remember about this new diagram is that the value of real money supply and demand increases downward away from the origin at 0 along the vertical axis. Thus, when the money supply "increases," this will be represented in the diagram as a "downward" shift in the real money supply line. The interest rate, in contrast, increases away from the origin to the right along the horizontal axis when rotated in this position.

Since the interest rate is identical to the rate of return on dollar assets from a US dollar holder's perspective, (i.e., RoR\$ = i\$), we can now place the RoR diagram directly on top of the rotated money market diagram as shown in the third diagram. The equilibrium interest rate, i'\$, shown along the horizontal axis above the rotated money market diagram, determines the position of the RoR\$ line in the FOREX market above. This combined with the RoR£ curve determines the equilibrium exchange rate, E'\$/£, in the FOREX market. We will call this diagram the FOREX/Money diagram.

International Finance Theory and Policy - Chapter 40-12: Last Updated on 1/11/05