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

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22 Bayesian FAVARs with Agnostic Identification<br />

is static 20 and allows for some cross-correlation <strong>of</strong> <strong>the</strong> idiosyncratic components, and <strong>the</strong><br />

dynamic version <strong>of</strong> Geweke(1977) and Sargent and Sims (1977) which assumes orthog-<br />

onalized idiosyncratic components. Their concept is mostly known as <strong>the</strong> generalized<br />

dynamic fac<strong>to</strong>r model and in <strong>the</strong> current literature also known as <strong>the</strong> dynamic principal<br />

component analysis (DPCA). Here <strong>the</strong>y do a principal component analysis <strong>of</strong> <strong>the</strong> first<br />

Q eigenvalues and eigenvec<strong>to</strong>rs which are calculated from <strong>the</strong> variance-covariance matrix<br />

(VCV) <strong>of</strong> <strong>the</strong> data set. The GDFM or <strong>the</strong> DPCA can be summarized as a concept that<br />

has a similar representation as <strong>the</strong> static fac<strong>to</strong>r model but with a dynamic setting with<br />

respect <strong>to</strong> <strong>the</strong> fac<strong>to</strong>r loadings.<br />

4.3.2 Two-Step Estimation<br />

This approach is analogous <strong>to</strong> <strong>the</strong> estimation procedure used in S<strong>to</strong>ck and Watson [2002],<br />

where <strong>the</strong>y used DFMs <strong>to</strong> forecast inflation. In order <strong>to</strong> uncover <strong>the</strong> space spanned by <strong>the</strong><br />

common components Ct = (F ′<br />

t, Y ′<br />

t ) ′ as a first step <strong>the</strong> first [K+M] principal components<br />

(henceforth PC) <strong>of</strong> Xt are estimated. Here <strong>the</strong> attentive reader should note that this<br />

first step does not exploit <strong>the</strong> fact that Yt is observed 21 Fur<strong>the</strong>rmore <strong>the</strong> number <strong>of</strong> <strong>the</strong><br />

informative variables N has <strong>to</strong> be large and <strong>the</strong> number <strong>of</strong> <strong>the</strong> PCs have <strong>to</strong> be at least as<br />

large as <strong>the</strong> true number <strong>of</strong> <strong>the</strong> fac<strong>to</strong>rs for <strong>the</strong> PCs <strong>to</strong> recover <strong>the</strong> space spanned Ft and<br />

Yt consistently. As a fur<strong>the</strong>r disadvantage one should state that <strong>the</strong> two-step approach<br />

implies <strong>the</strong> presence <strong>of</strong> ”generated regressors” in <strong>the</strong> second step 22 . Ft is obtained as<br />

<strong>the</strong> part <strong>of</strong> <strong>the</strong> space covered by Ct that is not covered by Yt. The advantage <strong>of</strong> this<br />

approach is that it is easy <strong>to</strong> implement and computationally simple as opposed <strong>to</strong> <strong>the</strong><br />

computer intensive burdensome Gibbs-Sampling approach. S<strong>to</strong>ck and Watson state that<br />

it also imposes few distributional assumptions and allows for some degree correlation in<br />

20 In this context, <strong>the</strong> static version <strong>of</strong> <strong>the</strong> fac<strong>to</strong>r model means that <strong>the</strong> common shocks only affect <strong>the</strong><br />

series contemporaneously.<br />

21 For our baseline model this means that <strong>the</strong> fed’s policy action is not taken in<strong>to</strong> account contempo-<br />

raneously.<br />

22 For more details please refer <strong>to</strong> BBE [2005].

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