1 Network analysis of the Italian Stock Market G. Rotundo Department of economics and management, University of Tuscia, Viterbo, Italy Galway, July 12nd, 2012 MP0801 Annual meeting
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Network analysis of the Italian Stock Market
G. Rotundo Department of economics and management,
University of Tuscia,Viterbo, Italy
Galway, July 12nd, 2012MP0801 Annual meeting
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References
G. Rotundo, "Centrality Measures in Shareholding Networks". In: "Use of RiskAnalysis in Computer-Aided Persuasion", Edited by Ekrem Duman, Amir Atiya, NATO Science for Peace and Security Series - E: Human and Societal Dynamics, Volume 88 (2011), pp. 12 - 28. ISBN 978-1-60750-827-4 (print) ISBN 978-1-60750-828-1 (online).
G. Rotundo, A. M. D'Arcangelis, "Ownership and control in shareholding networks", Journal of Economic Interaction and Coordination, ISSN 1860-711X, Volume 5, Issue 2 (2010), 191-219.
G. Rotundo, A. M. D'Arcangelis, "Network analysis of ownership and control structure in the Italian Stock market", Advances and Applications in Statistical Sciences, ISSN 0974-68119, Special Issue Vol. 2, Issue 2 (2010), 255-274.
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Network analysis of the Italian Stock Market
outline:
• Targets• Data sets and Network building• Control, ownership, and wealth• Control through the board of directors
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Companies in the Stock Market buy shares of other Companies in the Stock Market, so adding dependency among firms.
• shareholding networks
Targets: understanding the dependence among companies and the outcome for
• Ownership
• Control
• board interlocksBoard of Directors are not disjoint. Companies create ties
though common Board members.
Through the analysis of
Using methods proper of
• Complex networks, operations research.
Is diversification of shareholdings in companies portfolios a good proxy for the relevance of the company on the market with respect to ownership and control of other companies?
Detecting coalitions and oligopolies through portfolio diversification.
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Network analysis of the Italian Stock Market
outline:
• Targets• Data sets and Network building• Control, ownership, and wealth• Control through the board of directors
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The data sets/1: shareholding matrix• Companies traded on the Italian Stock Market (Borsa
Italiana) – 247 companies: shareholders and shareholding– 65 financial, 109 industrial, and 73 services companies – May 2008
• Data source: AIDA, CONSOB, BANKSCOPE (data on banks), ISIS (data on insurance companies)
• Threshold also below 2%• Data excluded: shareholdings via mutual funds (~0.01)
The data sets/2: board of directorsFor the same companies.
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Kout= 1 Kout=2 Kout= 3
A link is drawn from company i to company j if i holds shares of jOut-degree kout = number of links exiting from the node =portfolio diversification
i i ij1j1
j1
j2
j2
j3Direction opposite of
D. Garlaschelli, S. Battiston, M. Castri, V.D.P. Servedio, G. Caldarelli, The scale-free topology of market investments (2005) Physica A 350 (2005) 491-499
But the same of A. Chapelle, A. Szafarz, Controlling firms through the majority voting rule, Physica A 355 (2005) 509-529
The data sets/3: shareholding network building
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•The nodes of the network represent companies
•A link is drawn from company i to company j if
i holds shares of j
(the reversal direction of the one used in Garlaschelli et al.)
•The weight sij of the link is the percentage of shares of j holden by i. (the direction is the opposite of Garlaschelli et al., but the same of Simeone et al.).
Given cj= capitalization of j:
•Portfolio wealth vi= j sij cj=total wealth of portfolio of i
i
j
sij
Adding weight to edges
i
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Small connected components
Giant (weakly) connected component
(101 nodes)
232 connected components: most isolated nodes and
A strongly connected component inside the giant connected component (12 nodes) is the only responsible of cycles.
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•isolated nodes: in financial sector: 12; industrial: 77; services: 41•1-connected nodes: in financial sector: 27; industrial: 52; services: 29.•Most connected nodes:
name N. of different assets in their portfolio
insurance
banks
'ASSICURAZIONI GENERALI ' 19 'ALLEANZA' 15 'INTESA SANPAOLO' 15 'FONDIARIA - SAI SPA' 13 'MILANO' 10 'MEDIOBANCA' 9 'BCA GENERALI' 7 'BANCA MPS' 6 'AZIMUT' 4 'BANCA POPOLARE' 4
Hypothesis testing:Scale-free networks: P(kout) k-
Detecting P(kout)
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Comparison present analysis (MIB2008) Garlaschelli et al.
(MIB2002)• 247 assets• 56% of traded companies invest in
other traded companies
• Very close to power law
many companies decreased their diversification.
• 240 assets• 0.56 of traded companies invest
in other traded companies• No power law
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assortativity
Assortativity is a well known quantity that measures the tendency of high connected nodes to be connected with other high connected nodes.
The assortativity on the entire dataset gives 0.1659. This means that there is a weak tendency to form a high connected group
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Network analysis of the Italian Stock Market
outline:
• Targets• Data sets and Network building• Control, ownership, and wealth• Control through the board of directors
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Example: a controls x through
a chain of majorities
51%
51%
51%
51%
51%
a
c
d
e
f
x
DIRECT CONTROL
Ownership>50%
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IFIPRIV was born to finance IFIL to be the financial part of car producer FIAT and football team JUVENTUS
Example:
The chains of control are very short.
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A
B C
D
30%
20%
40%30%
60%20%
20%
Which is the percentage of shares of D holden by A?
DIRECT and INTEGRATED OWNERSHIP
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A
B C
D
30%
20%
40%30%
60%20%
20%+ 30%(60%)+40%(30%)
Which is the percentage of shares of D holden by A?
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A
B C
D
30%
20%
40%30%
60%20%
20%+ 30%(60%)+40%(30%)+40%(20%(60%))=54,8%
Which is the percentage of shares of D holden by A?
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A
B C
D
30%
20%
40%30%
60%20%
20%+ 30%(60%)+40%(30%)+40%(20%(60%))=54,8%
OWNERSHIP THROUGH INTERMEDIATES
DIRECT
OWNERSHIP
Which is the percentage of shares of D holden by A?
INTEGRATED OWNERSHIP
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A
D
ownership=
sum (of the products of all the weights) on all the paths from A to B
REMARK: weights <<1, then long paths are very close to 0.
Which is the percentage of shares of D holden by A?
INTEGRATED OWNERSHIP
REMARK: the presence of cycles is properly entering in the calculus of paths (cfr. Simeone et al, Chapelle et al)
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WARNING: ownership (biggest shareholding) is different from control
Example: a controls x through a chain
of majoritiesBut a owns only 3,45% of xMuch less than b (5%)
51%
51%
51%
51%
51%
5%
a
b
c
d
e
f
x
3,45%
DIRECT CONTROL
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wealthwealth of company i invested in the other companies in
the dataset
= j (the shares of j that i holds) * (capitalization of j)
A=matrix of shareholdingv=capitalization
wealth=A*v
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Questions:Is diversification of shareholdings in companies portfolios a good proxy for the relevance of the company on the market with respect to ownership and control of other companies?
Are the most wealthy companies buying more shares of the others just because of the higher level of wealth?
Answers:Correlation analysis among node degree, wealth, ownership, control
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Target: to build the shareholding network and calculate the correlation among quantities measuring portfolio diversification, ownership and control.
Portfolio diversification Network structure
capitalization Out-degree wealth ownership control
capitalization 0.3469 0.7006
Portfolio diversification
Out-degree 0.6751
wealth
Network structure ownership
control
Positively
CorrelatedOf course highly correlated
The companies that most diversify their portfolio are also the ones with highest wealth invested.
Questions:Is diversification of shareholdings in companies portfolios a good proxy for the relevance of the company on the market with respect to ownership and control of other companies?
Are the most wealthy companies buying more shares of the others just because of the higher level of wealth?
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Target: to build the shareholding network and to calculate the correlation among quantities measuring portfolio diversification, ownership and control.
Portfolio diversification Network structure
capitalization Out-degree wealth ownership control
capitalization 0.3469 0.7006 0.1446 0.15476
Portfolio diversification
Out-degree 0.6751 0.5696 0.818
wealth 0.2029 0.3650
Network structure ownership 0.7370
control
Also companies having small capitalization own other firms.
Also companies having small capitalization control other firms.
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Target: to build the shareholding network and to calculate the correlation among quantities measuring portfolio diversification, ownership and control.
Portfolio diversification Network structure
capitalization Out-degree wealth ownership control
capitalization 0.3469 0.7006 0.1446 0.15476
Portfolio diversification
Out-degree 0.6751 0.5696 0.818
wealth 0.2029 0.3650
Network structure ownership 0.7370
control
Many companies with a few links own other ones.
Due to companies having the only role to be the financial part of other company.
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IFIPRIV was born to finance IFIL to be the financial part of car producer FIAT and football team JUVENTUS
Example: Agnelli family
Chains of control are short (maximum length=2)
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Portfolio diversification Network structure
capitalization Out-degree wealth ownership control
capitalization 0.3469 0.7006 0.1446 0.15476
Portfolio diversification
Out-degree 0.6751 0.5696 0.818
wealth 0.2029 0.3650
Network structure ownership 0.7370
control
Out-degree is relevant for ownership much more than the total wealth
Out-degree is relevant for control much more than the total wealth
Is diversification of shareholdings in companies portfolios a good proxy for the relevance
of the company on the market with respect to ownership and control of other companies?
THE QUESTION
THE ANSWER On the data set portfolio diversification is neither a necessary nor a sufficient condition for ownership/control
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Network analysis of the Italian Stock Market
outline:
• Targets• Data sets and Network building• Control, ownership, and wealth• Control through the board of directors
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i
j
N.Common directors/N.directors in j
N.Common directors/N.directors in i
Corporate Board of Directors network
Out-degree kout = number of links exiting from the nodeNodes=companies
Companies i and j are connected if they have at least one Director in common
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Board sizeMean 10,25
Standard deviation 3,569Maximum 24Minimum 3
Directorships per DirectorMean 1,190
Standard deviation 0,585Fraction of directors sitting in n boards
1 2232 (87,56%)2 207 (8,12%)3 65 (2,55%)4 33 (1,29%)5 11 (0,43%)6 1 (0,04%)
• Board shareholding• Diameter 8 9• Assortativity 0.05 0.86
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( )p k k
=0.9689 (0.8068,1.131)
1( )P k k
=1.2717 (1.2139,1.3296)
( ) kp k e
= 0.4693 (0.3903, 0.5482)
( ) kP k e ( ) kP k e
= 0.7143 (0.6806, 0.748).
The Jarque-Bera test accepts the hypothesis of Gaussianity of residuals in all cases. Confidence intervals do not overlap:hypotheses rejected
Fast decay
Corporate BoardEmpirical analyses (connectivity, assortativity, ownership, control)
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Integrated ownership was introduced for ownership in shareholding network, but it counts votes: the approach can be repeated considering effective control, that is obtained by applying the majorization rule to the matrix of voting rights, i.e. formalizing the expropriation faced by the minority shareholders.
New information on the control of the market
Direct control may be achieved through direct ownership and board control.
Integrated control reports the control through controlled intermediaries (using the matrix of effective control instead of the original shareholding matrix).
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In the Italian market:Although Chain of control are short
Hidden relationships are relevant Social relationships are relevant
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Conclusions: on the Italian Stock Market
• Short chains of control
• Management through Boards
Work in progress:
• Market concentration