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Dynamic Macroeconomic Modeling with Matlab

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4 Numerical Simulation of <strong>Macroeconomic</strong> Models<br />

C<br />

1.01<br />

1.005<br />

1<br />

0.995<br />

0.99<br />

0 5 10 15 20 25<br />

t<br />

Figure 7: impulse response function for anticipated and unanticipated tax cut<br />

4.2.4 Numerical Calculation of Utility<br />

Consider a household that maximizes<br />

max U <strong>with</strong> U =<br />

c(t)<br />

∞<br />

0<br />

u(c)e −ρt dt (43)<br />

<strong>with</strong> per-capita consumption c, discount rate ρ, and standard utility function u(·). I define<br />

Ũ(t) =<br />

t<br />

0<br />

u(c)e −ρτ dτ (44)<br />

and assume u(·) to equal u(c) = c1−σ.<br />

Moreover, I define the balanced growth rate of c to equal<br />

1−σ<br />

γ and I define the scale-adjusted variable ˜c as ˜c := ce−γt . Then I get<br />

Note that<br />

Ũ(t) =<br />

Differentiating <strong>with</strong> respect to time yields<br />

=<br />

t<br />

0<br />

t<br />

0<br />

c1−σ 1 − σ e−ρτdτ (45)<br />

˜c 1−σ<br />

1 − σ e(γ(1−σ)−ρ)τdτ (46)<br />

Ũ(0) = 0. (47)<br />

˙Ũ = ˜c1−σ<br />

1 − σ e(γ(1−σ)−ρ)t<br />

(48)

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