Applications of state space models in finance
Applications of state space models in finance
Applications of state space models in finance
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10 2 Some stylized facts <strong>of</strong> weekly sector return series<br />
Technology<br />
Media<br />
Telecom<br />
Oil<br />
Travel<br />
Utilities<br />
Food<br />
Healthcare<br />
Insurance<br />
Figure 2.1: Hierarchical cluster dendrogram for the set <strong>of</strong> excess sector returns.<br />
or clusters — <strong>of</strong> observations with similar characteristics. Hierarchical methods like the<br />
one employed here do not require the number <strong>of</strong> clusters to be predeterm<strong>in</strong>ed. 2<br />
From top to bottom three major clusters can be identified. The outer left cluster<br />
consists <strong>of</strong> the three sectors Technology, Media and Telecommunications (TMT). The<br />
chart suggests that the TMT cluster is isolated from the rest <strong>of</strong> the market. This reflects<br />
the sectors’ outstand<strong>in</strong>g role dur<strong>in</strong>g the dotcom bubble at the end <strong>of</strong> the 1990s. The<br />
center group <strong>of</strong> sectors ranges from Oil & Gas to Healthcare and represents the defensive<br />
end <strong>of</strong> the market. The rema<strong>in</strong><strong>in</strong>g sectors constitute the cyclical part <strong>of</strong> the market. By<br />
mov<strong>in</strong>g the correspond<strong>in</strong>g subtree one level further down, one can differentiate between<br />
f<strong>in</strong>ancial and non-f<strong>in</strong>ancial cyclicals.<br />
2.2 Empirical properties<br />
Figure 2.2 displays the time series <strong>of</strong> orig<strong>in</strong>al prices, <strong>of</strong> excess returns as def<strong>in</strong>ed by (2.2)<br />
and <strong>of</strong> squared excess returns for the overall market and the two sectors Insurance and<br />
Food & Beverage. An <strong>in</strong>formal first look at these graphs suggests that the orig<strong>in</strong>al sector<br />
series <strong>in</strong> levels are trend<strong>in</strong>g. Formally, the existence <strong>of</strong> a unit root can be confirmed by<br />
an augmented Dickey-Fuller test or the Phillips-Perron test. As the existence <strong>of</strong> unit<br />
roots <strong>in</strong> f<strong>in</strong>ancial price series is extensively discussed <strong>in</strong> the empirical literature, the<br />
correspond<strong>in</strong>g results are not reported here; for a detailed outl<strong>in</strong>e <strong>of</strong> unit root tests,<br />
see, for example, Pagan (1996). In the follow<strong>in</strong>g, only excess returns will be considered.<br />
2 The dendrogram has been generated us<strong>in</strong>g the hclust() function <strong>of</strong> the open-source statistical<br />
s<strong>of</strong>tware package R 2.1.1 (R Development Core Team 2005) which can be downloaded<br />
from www.r-project.org. For an <strong>in</strong>troductory outl<strong>in</strong>e <strong>of</strong> cluster analysis and its implementation,<br />
see, for example, Struyf et al. (1996) and Kaufman and Rousseeuw (2005).<br />
Banks<br />
F<strong>in</strong>ancials<br />
Automobiles<br />
Retail<br />
Basics<br />
Chemicals<br />
Personal<br />
Construction<br />
Industrials