The relationship between DSGE and VAR models - cemmap
The relationship between DSGE and VAR models - cemmap
The relationship between DSGE and VAR models - cemmap
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Y t D 8Y t 1 C D" t (24)<br />
with<br />
8 D C A C 0 C 1 C 0 : (25)<br />
Proposition 3 (<strong>VAR</strong>(p)). <strong>The</strong> <strong>DSGE</strong> model (2) has a <strong>VAR</strong>(p) representation if <strong>and</strong> only if<br />
2<br />
3 1 2<br />
3<br />
0 1 : : : p 1 1 2 : : : p<br />
<br />
2 : : : pC1 D 1 : : : p 0 1<br />
0 : : : p 2<br />
0 0<br />
1 : : : p 1<br />
6 : :<br />
:: : : 7 6 : :<br />
:: : : 7<br />
4<br />
5 4<br />
5<br />
0 p 1<br />
0 p 2<br />
: : : 0 0 p 2<br />
0 p 3<br />
: : : 1<br />
where i D E Y t Yt 0<br />
i<br />
: In this case, the <strong>VAR</strong>(p) representation is<br />
h<br />
0<br />
Y t D 8 Yt 0<br />
1 : : : Y t pi 0 C ut (27)<br />
with<br />
<strong>and</strong><br />
E u t u 0 <br />
t D 0<br />
2<br />
8 D <br />
1 : : : p 6<br />
4<br />
2<br />
<br />
1 : : : p 6<br />
4<br />
3<br />
0 1 : : : p 1<br />
0 1<br />
0 : : : p 2<br />
: :<br />
:: : : 7<br />
5<br />
0 p 1<br />
0 p 2<br />
: : : 0<br />
3<br />
0 1 : : : p 1<br />
0 1<br />
0 : : : p 2<br />
:<br />
: : :: : 7<br />
5<br />
0 p 1<br />
0 p 2<br />
: : : 0<br />
1<br />
1 2<br />
6<br />
4<br />
0 1<br />
0 2<br />
:<br />
0 p<br />
3<br />
(26)<br />
(28)<br />
: (29)<br />
7<br />
5<br />
Ravenna (2007) similarly derives conditions for the existence of a nite order <strong>VAR</strong> representation<br />
of a <strong>DSGE</strong> model written in a different state-space form, which makes the distinction<br />
<strong>between</strong> endogenous state variables (W t ) <strong>and</strong> exogenous state variables (Z t ) explicit:<br />
W t D RW t 1 C SZ t (30)<br />
Y t D PW t 1 C Q Z t<br />
Z t D 8Z t 1 C " t :<br />
15