We know that real balances M/P are fixed in the short run, while the interest rate
is fixed at the level of the world interest rate r*. Disposable income is the only variable
that can adjust to bring the money market into equilibrium: hence, the LM* equation
determines the level of disposable income. If taxes T fall, then income Y must also fall
to keep disposable income fixed.
In Figure 12–22, we move from an original equilibrium at point A to a new equilibrium
at point B. Income falls by the amount of the tax cut, and the exchange rate
appreciates.