(our ear-lier assumption) or at a one-quarter lag (an extension of our
earlier assumption). For either of the three values of a121
, there is not much
evidence of an effect of anticipated tax changes on output. The
estimated parameter c0 varies from 0.07 for a121 5 0 to 20.03 for
a121 5 0.5, and is never signicant. There is a bit more evidence
of a positive effect of anticipated government spending on output. The coefcient on anticipated spending in the output equation
varies from 0.12 when a121 5 0 to 0.19 when a121 5 0.5, and, in
this last case, is signicant at the 10 percent level. Figure VI shows the effects, from quarter 0 on, of a tax shock
of 1 in quarter 1 under the assumption that a121 5 0.16, the
estimated sample average, or a121 5 0.0, or a121 5 0.5. It does so
by simulating the system of equations above (but extended to
allow for spending), in response to a shock of et
t of 1 at t 5 1. This
simulation is done under rational expectations: although the
shock occurs at t 5 1, anticipations of future taxes and output
affect output and taxes at t 5 0. For comparison, the gure also