The Balanced-Budget Multiplier
In the previous note, we showed that equilibrium GDP is governed by the following:
Ye =
x (a -bT + Ig + Xn + G)
where b is the MPC. From this relationship, we determined that the "multiplier"
for government expenditures is equal to
=
. Likewise,
the "multiplier" for lump-sum taxes is equal to
=
. More generally,
we see from the formula for Ye that D
Ye
=
x (-bD T
+ D G).
What happens if there is a balanced-budget change in government spending and
taxes? Substituting D T
= D G
to find D Ye,
we see that D Ye
=
x (-bD G
+ D G).
Factoring out the common D G
from the term in parentheses and rearranging, we find that D
Ye
=
x (1 -b) x D g
= D G.
That is, the change in equilibrium GDP from an equal change in government spending
and taxes is equal to the change in spending. Alternatively, the multiplier
for a balanced-budget change in G and T is equal to
=
x (1 -b) = 1.