This paper introduces costly investment into a stochastic equilibrium
macro model. Investment is determined by an endogenously determined To
bin-q that depends upon the structural parameters of the economy. The
model permits a sequence of economies, allowing for an increasing role
of government, to be studied. The effects of both a structural change
, taking the form of a higher variance of productivity shocks, and fis
cal policy on the equilibrium is analyzed, paying particular attention
to the impact on the growth rate and its variability. The role of the
Tobin-q in determining the response of the mean growth rate and its v
ariance is emphasized.