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Measuring the Effects of a Shock to Monetary Policy - Humboldt ...

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20 Bayesian FAVARs with Agnostic Identification<br />

identify <strong>the</strong> fac<strong>to</strong>rs and <strong>the</strong> loadings, separately, and fur<strong>the</strong>rmore distinguish <strong>the</strong> single<br />

fac<strong>to</strong>rs. In this <strong>the</strong>sis I follow <strong>the</strong> standard identification restrictions 18 ei<strong>the</strong>r on <strong>the</strong><br />

coefficient matrix Λ or on <strong>the</strong> fac<strong>to</strong>rs Ft employed by BBE in order <strong>to</strong> identify <strong>the</strong><br />

fac<strong>to</strong>rs and <strong>the</strong> fac<strong>to</strong>r loadings uniquely which looks like <strong>the</strong> following :<br />

Λ ′ fΛ ′ f<br />

N = I or F ′ F ′<br />

T<br />

The crucial assumption is that Yt (in our baseline model <strong>the</strong> policy instrument FFR)<br />

does not react <strong>to</strong> <strong>the</strong> X’s contemporaneously. The channels are restricted if <strong>the</strong> upper<br />

K × K block <strong>of</strong> Λ f is set <strong>to</strong> an identity matrix and <strong>the</strong> upper K × M block is set<br />

<strong>to</strong> a zero matrix. This restricts <strong>the</strong> impact <strong>of</strong> Yt on only those K variables that react<br />

contemporaneously and <strong>the</strong>refore such variables should be chosen for <strong>the</strong> respective block<br />

that do not react contemporaneously. Since fac<strong>to</strong>rs are estimated up <strong>to</strong> a rotation, <strong>the</strong><br />

choice <strong>of</strong> <strong>the</strong> K × K that is set <strong>to</strong> an identity matrix should not affect <strong>the</strong> space spanned<br />

by <strong>the</strong> estimated fac<strong>to</strong>rs 19 .<br />

For some proposes it is useful <strong>to</strong> separately identify <strong>the</strong> common shocks and <strong>the</strong> fac-<br />

<strong>to</strong>r loadings. But as only <strong>the</strong> product <strong>of</strong> <strong>the</strong> two is known, a rotation has <strong>to</strong> be chosen<br />

when one is interested in identifying <strong>the</strong> fac<strong>to</strong>rs and <strong>the</strong> loadings separately. In my case<br />

I am interested in <strong>the</strong> separate identification and in <strong>the</strong> following section I describe <strong>the</strong><br />

= I<br />

standard approach chosen by BBE that I also decided <strong>to</strong> choose.<br />

Digression on Fac<strong>to</strong>r identification In order <strong>to</strong> identify <strong>the</strong> fac<strong>to</strong>rs against rotation<br />

BBE impose <strong>the</strong> fac<strong>to</strong>r restriction F ′ F ′<br />

T = I, obtaining ˆ F = √ T ˆ Z, where Z are <strong>the</strong> first<br />

K largest eigenvec<strong>to</strong>rs sorted in descending order. In <strong>the</strong> joint estimation case <strong>the</strong> specified<br />

identification against rotation requires that <strong>the</strong> Fac<strong>to</strong>rs are identified in <strong>the</strong> following form:<br />

18 The fac<strong>to</strong>r identification should not be confused with <strong>the</strong> identification <strong>of</strong> <strong>the</strong> structural shocks <strong>of</strong><br />

e.g. monetary policy.<br />

19 see BBE [2005]

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