v - INFN
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v - INFN
Statistical modeling, financial data analysis and applications Venice September2013 Financial data Complexity: Dependency, Networks and Scaling Tomaso Aste Financial Computing & Analytics group • • • • http://fincomp.cs.ucl.ac.uk/ Academic Members Expertise: • Philip Treleaven big data analytics statistical modeling • Robert Smith algorithmic trading • Antoaneta Serguieva extreme market risk models high frequency trading • Sebastian del Bano Rollin price formation • Donald Lawrence behavioral finance • Denise Gorse market microstructure systemic risk • Guido Germano operation risk • Christopher D. Clack credit derivatives stochastic analysis • Tomaso Aste portfolio optimization External Members market microstructure • Guillaume Bagnarosa agent based simulations information flow • Ariane Chapelle news impact • Piotr Karasinski network theory financial mathematics • Jessica James statistical physics • William Shaw applied statistics MSc Programmes (….) • Financial Risk Management (~40 students) • Financial Computing (~30 students) • Financial Mathematics (~30 students) • (new) Quantitative Regulation / Business data Analytics Doctoral training • PhD centre in financial computing (~ 70 students) Information We are witnessing interesting times rich of information, readily available for us all. Using, understanding and filtering such information has become one of the major tasks and a crucial bottleneck for scientific and industrial endeavors Information content and flow are often associated with large degrees of redundancy both in time (repeating and scaling patterns) and across different variables (dependency and causality). Financial markets are information processing systems where news propagate and impact on orders, transactions and -ultimately- prices. Information impacts different operators and different products in different ways resulting in complex changes that can be seen at different temporal scales and across different financial products in a complex network of dependency. Financial Signals Complexity • Several time-scales of the processes • Large number of variables • Several kinds of interactions Complexity of each variable over its time evolution Complexity of the collective dynamics of all variables Scaling properties Dependency/ Causality structure Complexity of each variable over its time evolution Single variable Complexity 1sec-5min AAPL 1 sec data 3 Dic 2012 AAPL 1 sec data 3 Dic 2012 0 0 10 10 1 10 30 60 300 −1 10 −1 1 10 30 60 300 rescaled 10 relative freq relative freq H(2) = 0.34633 −2 10 −3 −3 10 10 −4 −4 10 −2 −1.5 −1 −0.5 0 lor−return 0.5 1 1.5 10 −1.5 2 1min-1h AAPL 1 min data Nov 2012 F> relative freq −2 10 −2 10 −3 −3 10 10 −4 10 −3 10 −2 10 −1 10 Log−returns 0 10 og-returns for the stock prices of Lehman Brothers (left panel) and reen lines mark respectively one, three and ten standard deviations l region with the power law function F> (r) ⇥ r . The estimated −6 −4 −2 0 log−return Log-return 2 4 1 2 3 4 5 6 7 8 9 10 12 15 20 25 30 35 40 45 50 55 60 0.5 1 1.5 −3 x 10 AAPL 1 min data Nov 2012 10 rescaled 10 −2 10 −3 10 6 −3 x 10 H(2) = 0.47532 −1 relative freq −1 −1 0 log−return 0 10 10 −0.5 Log-return/τH(2) 0 10 0 −1 −3 x 10 Log-return 10 −2 10 −6 −4 −2 0 log−return 2 Log-return/τH(2) 4 1 2 3 4 5 6 7 8 9 10 12 15 20 25 30 35 40 45 50 55 60 6 −3 x 10 Scaling and multiscaling: the observation of financial fluctuations at different scales (seconds, minutes, hours, days, months, years) reveals similarities and differences showing (non-trivial) connections between different time-scales Basic Materials Complexity across time-scales Quantification of scaling and multi-scaling K q (τ ) = x(t + τ ) − x(t) x(t) q q ~ g(q)τ qH (q) We developed a numerical tool to study directly the scaling properties of the data via the qth-order moments of the distribution of the increments: The generalized Hurst exponent method http://www.mathworks.com/matlabcentral/fileexchange/30076 When H(q)=H constant and independent of q the process is uniscaling or unifractal, H coincides with the Hurst coefficient or the self-affine index. When H(q) is not constant the process is multi-scaling (or multi-fractal) and different exponents characterize the scaling of different q-moments of the distribution. The nonlinearity of qH(q) is a solid argument against the Brownian, fractional Brownian, Levy, and fractional Levy models, which are all additive models, therefore giving for qH(q) straight lines or portions of straight lines. T Di Matteo Raffaello Morales, T. Di Matteo, Ruggero Gramatica, TA, “Dynamical Hurst exponent as a tool to monitor unstable periods in financial time series”, Physica A, 391 (2012) 3180-3189. Jozef Barunik, T A, Tiziana Di Matteo and Ruipeng Liu, “Understanding the source of multifractality in financial markets”, Physica A, 391 (2012) 4234–4251 M. Bartolozzi, C. Mellen, F. Chan, D. Oliver, T. Di Matteo and T.A, "Applications of physical methods in high-frequency futures markets", Proc. SPIE, Vol. 6802, 680203 (Jan. 5, 2008). Ruipeng Liu, TA and T. Di Matteo, "Multi-scaling Modelling in Financial Markets", Proc. SPIE Vol. 6802, 68021A (Jan. 5, 2008). M. Bartolozzi, C. Mellen, T. Di Matteo, and T.A, Multi-scale correlations in different futures markets, Eur. Phys. J. B 58 (2007) 207-220. T. Di Matteo, TA and M. M. Dacorogna, "Long term memories of developed and emerging markets: using the scaling analysis to characterize their stage of development", Journal of Banking & Finance 29/4 (2005) 827-851. T. Di Matteo, TA and M. M. Dacorogna, "Scaling behaviors in differently developed markets", Physica A 324 (2003) 183-188. Financial signal are multi-scaling log(K q (τ )) ~ qH (q)log(τ ) + log(g(q)) K q (τ ) = H(q) depends on q H(1) ≠ H(2) ≠ 0.5 multiscaling T O N . …. x(t + τ ) − x(t) x(t) q .. … r a e n i L q ~ g(q)τ qH (q) Deviations from pure Brownian motion are meaninghful T. Di Matteo, TA and M. M. Dacorogna, "Scaling behaviors in differently developed markets", Physica A 324 (2003) 183-188. 0.2 1996 1998 2000 2002 t 2004 2006 0.2 1996 2008 1998 2000 2002 t 2004 2006 2008 Multiscaling, switching and market stress Figure 3: Weighted Generalized Hurst exponent H w (q = 1) as a function of time for American International Group (AIG). Left panel: t = 200 days time-window. Right panel: t = 400 days time-window. The characteristic time is kept constant at ✓ = 300 days in both plots. The points are reported in correspondence of the end of the time-window. 0.7 0.7 American International Group 0.5 0.7 0.6 Htw (1) Htw (1) 0.6 Freddie Mac 0.4 0.7 Fannie Mae 0.6 0.3 2000 2002 2004 t 2006 2008 H tw (1) H tw (1) 0.5 0.4 0.6 0.5 Lehman Brothers Holdings 0.4 0.3 0.5 2000 2002 2004 t 2006 2008 0.4 2000 H tw (1) H tw (1) Figure 4: Left panel: weighted Generalized Hurst exponent as a function of time for American International Group (AIG). Freddie Mac Fannie Mae 0.7 0.7 Right panel: weighted Generalized Hurst exponent as a function of time for Lehman Brothers Holdings (LBH). Note the abrupt jump in the value of the GHE at the end of the time-period. The overlapping time-windows are t = 750 days, with ✓ = 250 days. The values are plotted in correspondence of the end of the time-window (solid black line). The shaded areas around the 0.3 0.3 0.6 plot represent the sizes of the standard deviations. 0.6 tick-line 2002 2004 2006 2008 2000 2002 2004 2006 2008 t t 0.5 0.5 interesting if we compare the two panels. According to [11, 12] these trends might suggest a transition from The wGHE is conveying important information about the stability of a company and by tracking its value in time one has a further tool to assess risk a stable stage of the companies to an unstable one. Other same trend are shown in Fig.6. Again the trend is increasing 0.4 bailed-out companies which show the w 0.4 Figure 5: Weighted Generalized Hurst exponent the H (q = of 1) as function of time. Left panel: Mac. Right panel: and crossing over the value of 0.5 towards end thea time-period when the crisisFreddie fully unfolded. Fannie Mae. The increasing trend over the whole period highlights a transition values of H w (1) < 0.5 tofinancial values of We have compared these results with those obtained by looking at otherfrom companies either from the w (1) 0.3 0.3 H > 0.5. This suggests a progressive change in the stability of the companies under study. sector or belonging to other market sectors to test the significance of these results. For example, in the Basic Materials sector,2002 we find2004 many companies whose dynamical wGHE in time, thus an 2000 2006 2008 2000decreases 2002 2004 2006exhibiting 2008 opposite behavior to that shown by the bailed-out companies in the financial sector. tAn example is reported t in Fig.7 where the dynamical wGHE’s for two companies belonging to the sector of Basic Materials are shown. We notice a very definite overall decreasing trend, as if the companies securities gained persistence Motors Washington Mutual Corp 0.75: General 0.7 Figure Weighted Generalized Hurst exponent H w (q = 1) as a function of time. Left panel: Freddie Mac. Right panel: 5 Fannie Mae. The increasing trend over the whole period highlights a transition from values of H w (1) < 0.5 to values of H w (1) > 0.5. This suggests a progressive change in the stability of the companies under study. 0.5 0.7 0.6 H tw (1) H tw (1) 0.6 General Motors 0.4 0.7 Washington Mutual Corp 0.4 H tw (1) 0.6 H tw (1) 0.6 0.3 0.5 0.4 0.5 2000 2002 2004 t 2006 0.3 0.5 2008 0.4 2000 2002 2004 t 2006 2008 0.3 0.3 Noble Energy Inc Occidental Petroleum Corp 0.7 0.7 of Figure 6: Weighed Generalized Hurst exponent H w (q = 1) as a function time. Left panel: General Motors, a company 2000 2002 2004 2006 2008Its bankruptcy was classified 2000 as 2002 2004 2006 2008 Right that went bankrupt following Chrysler in June 2009. the fourth largest in U.S. history. t t panel: Washington Mutual. The increasing trend over the whole period highlights a transition from values of H w (1) < 0.5 to w values of H (1) > 0.5. This suggests a progressive change in the stability of the companies under study. 0.6 0.6 H tw (1) H tw (1) Figure 6: Weighed Generalized Hurst exponent H w (q = 1) as a function of time. Left panel: General Motors, a company that went bankrupt fol lowing Chrysler in June 2009. Its bankruptcy was classified as the fourth largest in U.S. history. Right w (1) < 0.5 to panel: Washington The increasing the whole period highlights transition from values of in going through Mutual. the period of crisis. trend This over is in agreement with what ahas been considered asH the boost of values of H w (1) > 0.5. This suggests a progressive change in the stability of the companies under study. 0.5 0.5 turning away from the financial sector. the commodities market during the crisis, where investors were There are other sectors that have revealed instead no particular trend in the dynamical wGHE. We stress in going period sector of crisis. This is increasing in agreement with what for hasthe been considered as the boost of that eventhrough in the the Financial itself, the trend found bailed-out companies is not 0.4 0.4 the commodities market during the crisis, where investors were turning away from financial sector. common to others; for instance, many companies, like American Express Co andthe Morgan Stanley show There behaviors, are other sectors that have revealed instead no particular trend the dynamical wGHE. We stress stable with wGHE values steadily fluctuating about 0.5. We in will see in the next paragraph that that even in the Financial sector itself, thedynamical increasing trend are found theshowing bailed-out companies the sectors exhibiting a defining trend in the wGHE alsofor those extreme values is in not the 0.3 0.3 common to others; for instance, many companies, like American Express Co and Morgan Stanley show tail exponents of their distributions of returns. Although the increase or decrease of the wGHE is not simply stable behaviors, with wGHE values steadily fluctuating about 0.5. We will see in the next paragraph that related with the return only, behaviors are associated with the showing fluctuations of the log-returns the sectors exhibiting defining trend in the dynamical wGHE are also those values 2000 2002 a statistics 2004 2006 both 2008 2000 2002 2004 extreme 2006 2008in the distributions. tail exponents of their distributions of returns. Although the increase or decrease of t the wGHE is not simply t related with the return statistics only, both behaviors are associated with the fluctuations of the log-returns R Morales distributions. 6 Raffaello Morales, T. Di Matteo, Ruggero Gramatica, TA, “Dynamical Hurst exponent as a tool to monitor unstable periods in financial time series”, Physica Figure 7: Weighed Generalized Hurst exponent H w (q = 1) as a function of time for: Left panel - Noble Energy Inc.; Right 6 A,panel 391 (2012) 3180-3189. - Occidental Petroleum. The time-window is taken to be t = 750 days and ✓ = 250 days. Decomposing financial signals 3.48 3.46 3.44 3.42 3.4 3.38 3.36 3.34 0 50 100 150 200 250 300 350 400 Empirical Mode Decomposition 1.4 0 50 100 150 200 2 a (t) = Cτ (t) 1.2 250 2 H (t ) 300 350 400 (Hilbert-Huang Transform) 1 0.8 0.6 0.4 0.2 0 0 Instantaneous Hurst exponent 50 100 150 200 250 300 350 N Nava 400 Anomalous instantaneous scaling 2 log a (t) − 2H log τ (t) Log prices Log prices 3.6 3.625 3.58 3.62 3.56 Log Price Log Price 3.615 3.61 3.605 3.52 3.5 3.48 3.6 3.595 3.54 3.46 0 100 200 300 400 Time 500 600 700 800 0 100 200 Instantaneous var/period 400 Time 500 600 700 800 Instantaneous var/period -17 -15 IMF1 IMF2 IMF3 IMF4 IMF5 IMF6 -18 -20 IMF1 IMF2 IMF3 IMF4 IMF5 IMF6 IMF7 IMF8 -16 -17 var/period -19 var/period 300 -18 -19 -21 -20 -22 -23 -21 0 100 200 300 400 Time 500 600 700 800 -22 0 100 200 300 400 Time 500 600 700 800 Complexity of the collective dynamics of all variables Measuring dependency and causality X • Granger causality • Transfer Entropy • Partial Correlations Y Z Non-linearity and kernel measure • Kernelized Granger/Geweke’s causality • Hilbert-Schmidt Normalised Conditional Independence Criterion (HSNCIC) 8.2. Applying to financial data – Bitcoin • Kernelized Transfer Entropy Chapter 8. Application to real data Ensemble of methods TE bitcoin EURJPY TE EURJPY bitcoin 1.2 1.1 20 1 0.9 30 0.8 40 0.7 0.6 50 1.2 10 time window number, from 1 to 68 time window number, from 1 to 68 10 1.1 20 1 0.9 30 0.8 0.7 50 0.6 0.5 60 0.4 2 4 6 8 10 number of lags, between 0 and 11 SRE PRG 40 0.5 60 INF 1.3 1.3 0.4 2 4 6 8 10 number of lags, between 0 and 11 SRE − real stock returns INF − inflation rate PRG − production growth IRE − real itnerest rates IRE A Zaremba Information Filtering Collective Dynamics pi (t) 401 firms on the US equity market from 01/01/96 to 01/01/2009 data over a window of 250 days with 20 days steps stocks prices Dependency structure Ci, j = (x i − x i )(x j − x j ) x i (t) = log(pi (t + τ )) − log(pi (t)) ρ i, j = Ci, j σ iσ j N(N −1) = 80200 2 € I consider ρi,j as a similarity measure N=64 N=10 N=20 N=5 € € O(N2) relations with a lot of redundancy Distribution of eigenvalues λmax = 1+ 1 1 + Q Q λmin = 1+ 1 1 − Q Q € € € € p( λ) = Q= T N Q (λmax − λ)(λ − λmin ) 2π λ only order N are significant We must reduce connectivity without tresholding Simplifying Dependency Structure Information Filtering By keeping the network of important links only How can we build such a network? By embedding on a surface Why surfaces? • locally planar • natural hierarchy • elementary moves • computability Any network can be embedded on a surface! The embedding of KN is possible on an orientable surface Sg of genus (N − 3)(N − 4) g ≥ g = 12 ∗ any ΓN is a sub-graph of KN and can be embedded on Sg G. Ringel, Map Color Theorem, Springer-Verlag, Berlin, (1974) cap. 4 P. J. Gilbin, Graphs, Surfaces and Homology, Chapman and Hall, 2nd edition (1981) G. Ringel and J. W. T. Youngs, Proc. Nat. Acad. Sci. USA 60 (1968) 438-445. The surface constraints the complexity of the network € (the degree of interwoveness) Planar Maximally Filtered Graph max(∑ ai, j I i, j ) Sort similarities form the largest to the smallest Connect the first two nodes on the top line of the list i, j Delete the top line from the list no Is the resulting graph planar? yes no Keep the edge Discard the edge Have we reached the maximum Results number of edges? Guido Previde Massara, University College London yes [email protected] [email protected] Tomaso Aste, University College London Tumminello, TA, T. [email protected] Matteo, R.N. Mantegna, “A tool for filtering Tiziana Di Matteo, King’s College London tiziana.di [email protected] http://www.mathworks.com/matlabcentral/fileexchange/27360 M. information in complex systems”, PNAS 102 (2005) 10421-10426. Tetrahedron Maximally Planar Graph 5th September 2013 1 Results and discussion 1 1 0.98 0.96 0.8 0.94 0.92 0.6 0.9 0.4 0.88 0.86 0.2 0.84 0 0.82 (a) PMFG (b) (c) (d) Deltahedron heuristic BMPG (e) BMPG+T1 (a) PMFG (b) (c) Deltahedron heuristic (d) (e) BMPG BMPG+T1 Algorithm 3: BMP algorithm input : W — a correlation matrix output: BMP — a filtered version of W respecting the planarity constraint /* Initialise a triangle T1 e.g. by using the highest correlated vertices */ 1 T1 Three vertices with highest correlation ; 2 VertexList List of vertices of W not belonging to T1 ; 3 Calculate Gains(VertexList, T1 ) ; 4 n number of vertices in VertexList ; 5 i 0 ; 6 while i n do 7 (Vi , Tabc ) = argmax Gains(Vk , Txyz ) ; 8 Gains(Vi , :) = 0 ; 9 Gains(:, Tabc ) = 0 ; 10 Ta1 , Ta2 , Ta3 triangles created by the insertion of Vi ; 11 Calculate Gains(i + 1 to n, Ta1 ), Gains(i + 1 to n, Ta2 ), and Gains(i + 1 to n, Ta3 ) ; 12 Evaluate Gain by implementing T1 over Ta1 , Ta2 , Ta3 and execute 13 end 14 return BMP ; Figure 1: Execution times relative to PMFG of Deltahedron heuristics, DMPG,Figure 2: Sum of weights in the extracted planar graph relative to the sum and DMPG+T1 on a number of matrices: (a) Real correlation matrix 395x395,of the highest 3(N 2) edge weights of Deltahedron heuristics, DMPG, and (b) Real correlation matrix 395x395, (c) Real correlation matrix 395x395, (d)DMPG+T1 on a number of matrices: (a) Real correlation matrix 395x395, (b) Real correlation matrix 395x395 (e) Symmetric random uniform matrix 395x395Real correlation matrix 395x395, (c) Real correlation matrix 395x395, (d) Real correlation matrix 395x395 (e) Symmetric random uniform matrix 395x395 4 Results and discussion The novelty of the method is that we do not longer rely on any particular ordering but at 4.1 Analysis of the performance of the new algorithm with every stage we calculate the gain that would be obtained by adding any of the weighted measures remaining vertices inside any triangle, complexity is O(n2) and results improve PMFG G Previde Massara 1 We have tested the new algorithm for a number of matrices of various sizes and di↵erent composition. For every type of matrix we compare the time perfor- market. For each market day in t 2 [ t + 1, T t + 1] we peripheral stocks (with the largest values of X + Y ) and investigate the behavior of a selection of N = 300 stocks with built a portfolio with either uniform weights or Markowitz high capitalization and that have performed well over the preweights [4], with or without short-selling (in the present vious year ( t = 250 market days, see details in Materials and study this corresponds to a total of 7071 portfolios, with t 2 Methods). Specifically, we computed correlations over a win[ t + 1, ..., T t + 1]). For each portfolio we observe the redow of six months, reducing the excessive influence of remote turns, defined as rt (⌧ ) = [P rice(t + ⌧ ) P rice(t)] /P rice(t), market shocks on present correlations by using exponential over a year following the investment date (⌧ 2 [1, 250]). The smoothing [5] (which assigns higher weights to more recent performance of each investment strategy is measured by comevents and incrementally reduces weights to past events). We puting the average r̄(⌧ ) and the standard deviation, s(⌧ ) of then improved the estimator by computing the average correthe returns over the 7071 investment dates. We then used the ) lation matrix with shrinkage [6] over a period of six months ‘signal-to-noise ratio’, r̄(⌧ , as proxy for performance: good s(⌧ ) obtaining in this way a robust estimation of the correlations over the year preceding the investment day t (see details in Materials and Methods). Such a matrix shows a remarkable F Pozzi persistence, with autocorrelation values ranging around 50% 1.0 1.0 P m= 5 m= 10 P even after one year1 . This high persistence is a very impor0.8 0.8 tant fact implying that measurements from the past are likely to forecast the future and the ordering of the correlations is P 0.6 0.6 expected to remain rather stable. We then used these average r̄ r̄ weighted correlations with shrinkage s s C to construct the financial 0.4 0.4 filtered networks: M ST and P M F G [2, 3, 7]. An example of C C P M F G is shown in Figure 1. C 0.2 0.2 We now discuss how an efficient investment strategy can benefit from the knowledge of such market dependency struc0.0 0.0 0 42 84 126 168 210 252 0 42 84 126 168 210 252 Market days Market days P ture. In particular we built portfolios from a set of stocks Portfolio performance C 1.0 1.0 selected from the peripheral regions of the financial filtered m= 20 m= 30 networks and we compared the performance of these portfoC 0.8 0.8 C lios with the performance of Cportfolios built from Ca selection C C C of central stocks andC other portfolios made with randomly se0.6 0.6 C or built by using other traditional methods. lected stocks To C r̄ r̄ C s s C C this purpose, we first must distinguish between stocks lying in 0.4 0.4 the networks’ central regions from those lying in the periphC C C eries. Numerous centrality/peripherality measures have been 0.2 0.2 C P proposed in the literature [9, 10, 11, 12, 13]; they reflect difP P happen that a vertex results central 0.0 0.0 ferent criteria and it can 0 42 84 126 168 210 252 0 42 84 126 168 210 252 Market days Market days C for one measure and peripheral for another. We have thereP fore adopted an ‘agnostic’ perspective by looking at some of Fig. 2. Comparison between the performance of di↵erent portfolios with uniform 6 6 6 the most common centrality/peripherality measures (namely P weights (u) composed of m = 5, 10, 20, 30 stocks. The symbol ⇤ indicate portDegree (D), Betweenness Centrality (BC ), Eccentricity (E), folios made with m most peripheral stocks (i.e. with largest X + Y ). O indicate 85 85 85 C portfolios made with the m most central stocks (i.e. with80smallest X + Y ). These Closeness (C ) and Eigenvector Centrality (EC ) [13] and P by 80 80 performances are compared with: (/) portfolios made of m randomly chosen stocks; combining them in order to better identify central and pe75 75 75 (.) portfolios made with the 70 m stocks that have achieved70the best performance over 70 ripheral stocks in the financial filtered networks. Specifically, C P the period preceding the investment date. The (tick line) is a ’market portfolio’ made we constructed two hybrid centrality indices, X and Y , which 40 is the same across the four 40 MKT it MKT MKT by40 taking all 300 stocksP−pand figures. P−p P−p 30 30 30 group together the rankings of the previous measures (see deM−p M−p M−p 20 20 20 PM−p PM−p PM−p 10 10 10 P−c P−c P−c tails in Materials and Methods). In terms of these hybrid 5 5 5 M−c M−c M−c PM−c PM−c PM−c C 1.0 1.0 measures, Csmall values of (X + Y ) are associated with central Probability of negative returns m= 10 m= 20 Pvertices whereas large values are associated with peripheral P 12 12 12 0.8 0.8 vertices. From the study of the variation with time P of these C C 85 85 85 centrality indices we observed that central vertices are sta0.6 0.6 80 80 80 C P ble with a large likelihood to be persistentlyP observed in the r̄ r̄ 75 75 75 s s P center over time. Whereas peripheral vertices tend to be less 0.4 0.4 70 70 70 stable with a larger variability. [un po’ di piu’ e un po’ piu’ 2 40 40 40 MKT MKT MKT 0.2 quatitativo ] We observe that, in terms of industrial sectors , P−p P−p P−p 30 0.2 30 30 M−p M−p M−p 20 20 20 PM−p PM−p PM−p 10 10 10 the peripheries are mainly populated by companies belonging P P−c P−c P−c 5 5 5 M−c M−c M−c 0.0 PM−c 84 PM−c 0.00 PM−c 210 0 42 126 168 210 252 42 84 126 168 252 to “Electric, Gas, and Sanitary Services” (representing 20% Market days Market days of peripheral companies vs. 11% of all companies), “Oil and Fig. 5. Probability of non negative returns (expressed in per-cent values) after six months from the date when the investment was made (upper panel) F. Pozzi, T. Di Matteo, and TA , “Spread of risk “Petroleum across financialRefining markets: the peripheries”, Reports 1665. Fig. in3. Comparison between performance di↵erent portfolios obtained (ns by) and wi Gas Extraction” (7.0% vs. 4.8%), and from the better date whento theinvest investment was made (lower panel). TheScientific cases the with uniform weights (3 uof ),(2013) Markowitz solutions with no short-selling Efficient diversification / risk hedging Correlation networks can be used for efficient portfolio differentiation by selecting stocks from the periphery of the PMFG P . . . . . . . . . . . . . P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P . . . . . . . . . . . . . . . . . . . . . . . . . P . . . . . . . . . . . P . . . . . . . . . . . . . . . . . . . . . . . . . . . u ns s u ns s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P P . . . . . . . P . . . . . . . . . . . . . P . . . . . . . . . . . P . . . . . . . . . . . . . . . . . . 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BEV HPC ADBE ETR HAL NSC HRB GLK CA MOT CINF BGEN LPXHOG RF2 CGP WCOEQ LLY MUR 68335Q BMET MDR MYLMCI FHN INGR HCA MU GS KMRTQ FJ HDLM OMX BAC DLX NSMNL FITB GCI BUD EK F CMI BR BC GFS/ CCK ECO CISCO GR MYG CRAY AZA AFL CIN FLS NSI MWV MALK IPG HM BOL ASH ONE AAPLDCNAQ DTE NEM AGC N IMNX WB BSET AR BW CSCOLEG MN JH DWD RRD ECO ARB CVX GFS/ CBE GR ECLHNW GDW SNI AGN CINF HTMXQ BWS MHP G FPC MRM ASO MU MIL KMG GWW BRNO ABS SA LIZ ADCT HDGD BMG H BEN ADCT C 1132Q MDRCIC AA ALL HLS HD AVP FWLT GTEC BLL CHIR OMX CIN ALXA MMM CTL KSE HTMXQ AMD DUK VZ HRZI ADP DWD CHRS TGT JPM EP AYEPHA AI LSI DALRQNRTLQ AL HOU CSX ITW BAX KSE AZA 0.3 ABS KMG BEN AA MALK UCM BMG FLE HAS GMADCT BMG ASH KSE WYEFLE ABS SA IPGBRNO GWW GR RYI MZIAQ HM CTL ALL FTLA LIZ ALL AMGN FLS CNW BEN SA KMB AZA RF2 GPC HD CBE ASO FLS LIZ ASH MZIAQGM PGN KMG UCM 0.4 FRX HRB CBE GWW IPG BRNO NKE DELL EC 0.2 MSFT TAP JPM DPSJWN DTV BOL BAX PHA 1132Q D KEYMI AOC BSC DE BNI ARCINF MOT NC DLX LDG DG GAS ABT HTMXQ DOW GT EQT 2004 2006 2008 JEC AM BSETHRS AGC T. Aste, W. Shaw and T. Di Matteo “Correlation structure and dynamics in volatile markets”, New Journal of Physics 12 (2010) 085009 1-21. T. Di Matteo, F. Pozzi, T. Aste, "The use of dynamical networks to detect the hierarchical organization of financial market sectors", Eur. Phys. J. B 73 (2010) 3–11. Complexity reduction: DBHT We extract clusters and hierarchies form the PMFG in 5 main steps built around the properties of 3-cliques in maximal planar v4! graphs v4! Won-Min Song, T. Di Matteo, TA, Nested hierarchies in planar graphs, Discrete Applied Mathematics 159 (2011) 2135-2146. k2! {v2,v4,v5}! v4! k1! {v2,v3,v4}! v2! v7! v5! v2! v9! 3-cliques v8! v6! v5! v2! v3! v4! k3! {v3,v4,v6}! v6! v3! v3! Some cliques contain inside others providing a natural hierarchy Example of PMFG for Eurodollar rates 3-cliques on Maximal Planar Graphs have a unique property: They contain other cliques inside or/and they are contained inside the other cliques. Eurodollars ≥ 2 years 16 interest rates with maturity dates between 3 months and 4 years. T. Di Matteo and T. Aste, "How does the Eurodollar Interest Rate behave?", Journal of Theoretical and Applied Finance, 5 (2002) 122-127. (arXiv:cond-mat/ 0101009, 2001). < 2 years DBHT The clique structure provides automatically a classification into communities organized into a nested hierarchy v5! v4! v4! v7! v5! v2! v6! v7! v5! v8! b3! v7! v2!b3! v 4! k 2! v6! b2! v8! b1! v3! v2! v3! v1! v2! v4! v2! v4! k1! v3! k3! ! α v v3!v5!6! v9! k3! v4! v6! b4! v8! v3! ! β b 2! bα= b1! k1! k2! bβ = b4! Directed Bubble Hierarchical Tree v1 ! v2 bα! ! v3 v5 b2! ! v4 v6 bβ! ! v8 v7! b3! ! We capture both local clustering and global hierarchical organization without introducing any characteristic scale Won-Min Song, T. Di Matteo, Tomaso Aste, Nested hierarchies in planar graphs, Discrete Applied Mathematics 159 (2011) 2135-2146. W.M. Song, T. Di Matteo and T. Aste, “Hierarchical information clustering by means of topologically embedded graphs”, PLoS ONE, 7 (2012) e31929 WM Song Clustering and Hierarchy - DBHT PHA PMFG-DBHT 16 clusters CBE NL CN BNL MS BW HLT CY KO FITB MYL NRTLQ DOW CVX 1132Q GS BNY CI AL ITW WCOEQ H HRB F APA GENZ AOC BMC AMAT AVY MUR CL BUDHOG D HP OMX INGR DE CLX WB AGN BSET BAX AMOT AR ACKH ABS BMG CINF NC HNW GWW HM BMET BSC FTLA SNI ECL AGC BOL FLE AIG AAPL MER ASH DTE KSE MZIAQ BFO CAR AM HOU DTV GPBGEN HRS 1357Q NSC CMA BMY SA LLTC CAT ADM IP GDW BF/B IFF DJ HCA LIZ KEY IPG ABTWFC DCNAQ ADBE MI AH FDO KMRTQ GM GLW KBH CA ETR HPC N MAS GR GPC DELL GPUI IKN ADCT CMS HPQ LPX CGP BC MDT BLS ANDW JEC EDS APCC FISV NBR ETN BEN BMS AM A USB HAS CSX HES JO LSI AFL HON NSI NSM THC CPQ MU KMG CTL CCK AEP GIS CIN CYL IR MDR HAL BDX CAG CMCSA APC HLS FO MCD WYE CIC JCI MRK CB 68335Q MMC BK T HBAN MEL CS GLK HD GD IGT ACV AMR ADSK BEV MCI KR CMI BHMSQ CR DIG BAFLTWQ BR GR CH LLY GCI GAP ALTR BJS NKE ENRNQ NAV GE MEE FRX BBS APD PGN EMR DALRQ CCTYQ AXP ADI MYG NOC RF2 MAT FHN PKI NEM EK ABX CTAS HDLM KSU CPB IBM L KRI EQT CNP MWV IMNX BGG CRAY AI HRZI KRB FLMIQ FPL ED NCC HST MDP BHI LDWI AVP JH GFS/ EP BA DHR ALXA MMM NWL MO K BCR CSC GPS CTX AA BF/ABDKEFU DWD ALL HUM RYI MN DD CHRS DLX MHP ADP JP AYE GRA BNI MRM DG RRD FWLT HSY MI CAH CCE CNW JNJ G ARB MAY MOLX LOW CSCO LEG ECO HNZ BWS BAC JPM LO GTEC AMGN MALK JPM MIL NBL XOM TGT JWN FDX MIVZ LUB FPC ONE CVS NI INTCAS HI RHDC GAS DPS FMC DUK BLL FLS VVI MT CHIR LUK ASO BRNO UCM LDG 401 stocks on US market 1996-2009 NTRS CTB AMD GTFRE DG LNC HTMXQ CEG FJ FC TAP LTD MSFT AET KMB DDS AT FNM EFX NMK KW EC DOV AZA 16 14 12 10 8 6 4 0 2 0 RAGAK VCBPZCCIRCTNHC SIHCSAGCOMAIA RITDNPLCA RMPBGTCIEDDCNBCAC KA/SFYPFETM U CQISKAEPMLG YEMKKI LYRDPAHBJ C SINVUBAH PTMCMC NE D IPEHQYRANRKCMRI LXAI NEBLDHL WZTPPNSRDWOHTGALDR ADTGUDBH CBCN CDCRKCDSECR G DPCDHRPCMFE G OLOWLMEOBLNBM CYGXSARWAMAMLC MHNBWJMCDDS ISONPJTJ PJNJINFAAWMLF SV DCEZTNLPOJC OIHF XMRMDEWTCFG TTGCLLBVFENCG CSSUANDI CKIGMRTDCTLLN SBTNVFL C EIKVGRU A DLGTLFMDBSMMTH QTFXRN MK2SARRJSBNMF A VXLPLDBFN WS JE CG R/LIASEXCMGFMABM PVRWMUK SBSZAB RRUGACTMGAE UE D STMDF NF TVMKOAOMENEDKCD CF WQBXINPGAKSAENAHA NLCNDG WFWETNBTIDAAIC AGAAM TWBMROEWGBSBAB CTCRDSBCHA E HNSLOLMKCCB XSNH A THLELCBUBLDKBH DLGPO XFPNA31 ALPQXGMU75HMO BRRMCGBCW TWCCQASFELENBOG OPNH OZIYYCTVNCKICBF BXGMB 6 VSLARYEBAK5G3BB3HMI8K NQL/FRN QAKRBMGGKTWMICC NF RCPEOI MH TNPRDEDBACNBMC RSXXLSISGECNCD ALEKAJLL CGOCTIEBJ CXPATNHDFI NVMMBBA RCMH CIBCPIALAD QNSFAFARLRMHDPCHAB YMCSECEAHGB B AOYNHCMDDSEMHMF HF SP RQDHDT L QCJSISABWLHBAC CM CHSRLMOAEKCA DI ETM TYUYNLAAVO2AT3PH1R1N QAQHLOTID WWBM AEKEHDIDZAM QRTECBYAGKAWB MESSBMCAB MZTEGIESDLWMG WMARGGHF DL HK SEGUAPMPGG DICHVLSHSNTIABIRFFB AGNOFEPGAM ILCYA DIGSXPNBCLA AH A XTPI QBTJAELF ILMLIMM MQLASTALGMMCHMP TDNLAYGCPCCC A NIQENMHLIGAAMUM MIK SCMXC WYOLMISLONFH S GKAA CHNTCRCRCIZCPBV AIMOCACSSI ANCLAGNPDRHPTI D CCABCDECSTIMGBR MGTEPFMYF/KQUKA PCI CHBJALPDEYLASKEYI HABURVNMKS ENMCCDMTPI RCR E IMDKNABRYQHPII LHNELXAL DRGAHTOWDRNSWPPTZ HBLDUGDBAT NCCCCR SCK MRFDREHGDCDD EP NMOMCWGOOCP LB EALXL MAMWG CLSDMRAJMHCSBY DCWN JTJWPANNOSJII FP OLMNAVTFNCSZJ CJPL ED GFCTWFHEMDIMORXT GDCNEAVFBLGCCSLT NILNTDUTMCSKI CLNRTGS FLVUVCB HTMABMDGRDKETI MRSXFLGL NMSFQT2 ANFNBFRRAJMSXK BDPLWVL GEMJCCS MBMAWFGXESRAPLI/ UKAMSRSV BEGCZUAB AMTGRR NFDMFDEOUST DCKDENMEOFAMCKVT AHANEASKGANWQXBI GCDANDCTPWNL AINBWET MAIGF BABSWBGAOWMRAT AHCBDSROECCEBT CCKNHSL ABDKBHMBNLLSXL HLOUBCHDET 13APNPGXFL OM5G L WCBGHCMMUR7QRXPBA GONBEELHFSAWQCCT NO FBCICKNCOPYZI 6 MBGVTYXB K8MH3BBG3KAB5EYRASVL INCRFGTL/QNBK WHMCIMGKFQNRA MOECRP CMNCBADBEDIRNPT DNCEGSSIRXXS LCLAKJLGEAL J TO BECC FDIBHNATICPVX ABMN DAHAMCPCMRB HCMDLIRAFQCNFI ABPHRLEAMS BH GBHFMCAECHNCSY E FLMMHDSPDDQOSYA TBWHDRJ CAHLMBASCCQSI COSL AKEAMRHC N1R1HMA3OTEVAANDYTI DPTOH2LQQUAYL ITW MAZMDDHBEWKEA WIAYCRT ABKGSBMQE BGAMCMDLBGEES WHSEWIMATZ GMR GKGHFPMGALDES BFRFAIHSPUGCDI BTINPSLOHV MAGEFGNAL AALNYPCGDI CABXHSAI FLEAQBTJPXTI MCMMALMIQLI PMHGLTMSAL AMCCCGPCYAQNDELT MUAGMIN CXAMNCSLHMONKII HFOSWMIL LSY 4 6 8 01 21 41 61 2 50 100 150 200 250 300 350 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 G KR AP C BV CHNATCRC C AIZC O SSI AIM C H G ACD T LAN PTIDR BPRI ABNC G CC M DEFEC S TPYF/U K MG A MPKQ I S EYLAC CH JBALPD I K KSEY HABURVNM CC ENM TPI DYM E RCRA PI H IMDKNN Q R BLALI LAH ENX HOD PZ SW R RDG W T P LD ATT GD H U B B N C CC R C K S C D RDEG M D D PHG EFCR CP MNOM O OL LW L B B E X AG MW A SBY RRAC CLMSDM H DJCPJWM N JTWANNOSJII F AFN SZPJ OLM VTC ED CJFHPN LM DIO GFCTWEM R XT CNEVFBLG G SLT AC DNU C S I NLTDTMC K RTGSI LC LVN B F U RVC KEI G HTMABM DTL SDXFLG MR NSFQT2 M FNBRJM SXKV CAINSBFDRAPLW C SL J E O GFM CCR AI AG S E MBM X PL/ MRS UW V SZU B BKEAGC A R AMTEG R U T NFDM FDAOS D N KT OM DCKEM E V C F K B N X AHAEASG APNW Q NLI C G D AN CD ET W BTW IAN G MAAOIM AF R BABSB W W G BT C SREC AH D CBC ESTL O K CLN H XL ABD S KBHM BBNLH HLOU ELT CG D P 13O5ANPXF G M 7 XPLA HM U WCBG RQ R M B C N AC GOBEELH CT FSNW Q O P KNCOZI C FB CIG B BKVETYYX 6 H3M S B K8M R 3FAB AVL 5LQ N IB RG N C /R BK M CG W KTFQ G M N HMIO PA E C R AEDIR N B CMN PT D X DC CGBSSIR X S L K LCNE A EAL G JLEJTO C B C N I PX FDIBHATC V N ABM R DAH AMC B LDIRPAFCC HCM NFI Q S LEAM PHRC BAG SY A BH BFHM C ECH N E D A M Y DO HS FLM S P D TTBW R HDQ J C L CAHM BASCQ SLI CO S C A H MR AEE D ATVAAN N1R1HKM YYTI O 3 T L 2 P U DOHLQ A ITW W M MAZDDHB A K E WIAYE CQ R T AGB E K B M CM S BGAM GEE DLBSEIM WHSW ATZ G R GLM HFM D GKG E AS PUG BFR FAPINH I C S D H VA BATIPESLO N MAGYFCG L I ALNPG SD CBXBTH A AXII E Q FL AJMPT MALIQLI MC HM A PM TM G M SLT C CLYAN D AMMCCG P EL IQ N GLM N I HM C CXUAHAM S K IOLI OSW FN M LSY 10 8 6 Kruskal-Wallis test p-values 0.000000 Energy 0.000000 Financial 0.000000 Technology 0.550930 Conglomerates 0.000001 Consumer Cyclical 12 oil industry energy exploration & services mining energy production & distribution rail roads retailers & consumer products car & transportation pharmaceutical health beauty beauty food semiconductors electronics computers telecommunications banks retailers 14 constructions 16 finance & banking meaningfulness 4 2 0 Two main factors contributing to financial data complexity: Complexity of each variable over its time evolution Complexity of the collective dynamics of all variables Are them related? 3 Are dependency Hierarchy and Multifractality related? he hierarchical order is defined as the cardinality of i , ni = card( i ). In the example reproduced in e stock labeled by i,T.we 2, 4, 5, 8, 10}, i = {a , a8 , aScaling set of nodesof Financial Time Series Are Related i = {1, 1 , a2 , a4 , a5and 10 }, i.e. the R Morales, Dihave Matteo, TA, Dependency Structure Properties red dots and ni = 6. q-fin arXiv:1309.2411 Hierarchical order e of hierarchical structure. The path highlighted in red is Multifractality ΔH=H(2)-H(1) i, while the thick red bullets are the nodes R Morales H(1, 2) = H(1) H(2), (1) 0.8 r q = 1, 2 is the generalised Hurst exponent computed from the linear scaling of the empirical16q-moments Section for more details). We have removed from the analysis all stocks whose multifractality cannot 14 y distinguished from zero, which correspond to weak multifractal behaviour and hence would not be 12Methods). s context. The benchmark value for multifractal stocks has been set to H(1, 2) > 0.015 (see 0.6 0.4 !ρ" t N c ,t Dependency Hierarchy and Multifractality are related! 10 0.2 6 8 Financial Sector Industrial Sector 0 6 0.05 0.04 2006 t 2008 2010 −0.2 2012 0.035 0.025 8 10 12 14 n 16 2004 8 0.035 Cluster no. 2 14 2006 t 2008 2010 2012 !n" t 0.025 0.04 0.015 0.035 0.02 0.03 8 10 12 14 16 18 n 14 16 14 16 Cluster no. 3 0.02 0.01 120.035 0 0.03 110.025 −0.01 0.025 0.02 −0.02 0.015 0.02 10 0.015 0.015 6 12 0.03 0.04 0.045 ∆H(1, 2) !∆H (1, 2)" t ∆H(1, 2) 13 342 most capitalised stocks continuously traded in the NYSE in the period 2-01-1997 to 31-12-2012. 10 0.045 0.03 0.05 0.02 !∆H (1, 2)" 6 4 2002 0.03 0.025 FIG. 4. Coalescence of the hierarchy in time and dynamical correlation. (Left) The number of cluster Nc,t as a 0.03 function of time is plotted in time in blue empty circles. The dashed red line is the best fit over the entire time period 0.025 2-01-1997 to 31-12-2012, while the magenta line is the fit over the shorter period preceding the 2007/2008 financial crisis 0.02 0.05reported as too small to be visible. (Right) September0.02 2002 through November 2007. Standard errors on the circles are not Dynamical evolution of the average correlation (thick dots) in the same time period. The dashed coloured lines represent the 0.015 0.015 2.5%, 25%, 75%, 97.5%-quantiles, taken from the distribution of all the observed correlation coefficients. 0.04 0.03 !∆H (1, 2)" 2004 ∆H(1, 2) NYSE 0.035 4 0.045 2002 ∆H(1, 2) 0.035 20 0.01 8 10 12 14 16 −0.03 8 18 10 12 5 200610 20 n2008 15 2006n 2008 2010 2012 2002 2004 2010 2012 t t FIG. 3. Correlation between multifractality and hierarchical order inin single sectors and clusters. We plot in black FIG. 3. Correlation between multifractality and hierarchical order single sectors and clusters. We plot i dots H (1, 2) against the hierarchical order n for stocks in the Financial (top left) and Industrial (top right) sectors and cluster dots H (1,22) against the hierarchical orderright). n for In stocks in the Financial (top left) and Industrial (top right) sectors (bottom left) and cluster 3 (bottom all plots the blue line is the best fit of thediamonds dots, while the red squares are theand 0.04 FIG. 5. Average multifractality and hierarchical order in time. (Left) The blue are values of the average 0.12 5. Average multifractality hierarchical order in time. (Left) The blue arethe values of the 0.07 2 (bottom left) and 3 for (bottom right). In all plots the blue line is the best fit of thediamonds dots, while red squares averages ofcluster H (1, 2) each and fixed order. 0.05 FIG. over 50 overlapping time windows. The dashed green green line the best fit over the entire period onstration that multifractality and hierarchical order are positively correlated. (Color We averages ofmultifractality H (1,online) 2) each fixed time order. multifractality over 50for overlapping windows. The dashed lineis is the best fit over the time entire time2-01-1997 period 2to 31-12-2012, while the blue line is the fit over the shorter period preceding the 2007/2008 financial crisis, September 2002 cles with error bars the multifractal indicator h H(1, 2)i averaged over sharing through the same hierarchical 31-12-2012, while the blue line is the fitred over theareshorter preceding the order 2007/2008 financial crisis, Septemb 0.04 thetostocks November 2007. (Right) circles values ofperiod the average hierarchical over 50 overlapping time windows. 0.035The 0.06 C. A Multivariate Dynamical Hierarchical Model through 2007. The circles values of the2-01-1997 average to hierarchical orderthe over overlapping the hierarchical order n. The blue solid line is the linear fit over the averages, while the November orange horizontal dashed 0.1 The dashed green line is the bestred fit over the are entire time period 31-12-2012, while blue50 line is the fit overtime the w p (Right) dashed greenFigure line ispreceding the best fit2007/2008 over the entire time period 2-01-1997 to 31-12-2012, while the blue lineerror is the fit o period the financial crisis, September 2002 through November 2007. In hierarchical both plots the bars limit up to which the increasing trend is observed. The error bars 0.03 are theThe standard errorsshorter computed as s/ N, from LSE (see 3 in SM). The two Asian markets show a much wider range of order due p In order to explain the mechanism underlying the observed link between multifractality and correlation hierarchy we are the standard mean error on0.03 thefinancial mean s/ crisis, N , withSeptember swhose the standard deviation. shorter period preceding the 2007/2008 2002 through November 2007. In bothThis plots thebia err appearance of one very large hub in the correlation network, which includes most the stocks. hub standard deviation over the stocks having same hierarchical order. introduce a dynamical hierarchical model (DHM), main novelty with respect to of standard multivariate models 0.05 !∆H (1, 2)" !∆H (1, 2)" n TSE detrended TSE LSE !∆H (1, 2)" 2004 HKSE p !∆H (1, 2)" n order Hierarchical 2002 [5] in theerror introduction of a order. perturbation term on correlation matrix associated to can its hierarchical structure. evaluation of lies the proper hierarchical bythe detrending the time series we remove the large hub the standard mean on the mean s/ NHowever, , with s the standard deviation. 0.02 are 0.08 model returns of stock as forWe TSE data and only fori the at least small hierarchical orders, retrieve a similar behaviour to that observed in p volatility 0.025 Figure 5 in factor Supplementary Material). As explained in detail in the SM though, detrending the series se igure 20.04 the mean value h H(1, 2)i with standard error s/ N0.01 (with2s (see the standard deviation on theas ri,t = ✏Y (2) i,t i,t , scaling properties of the data and the overall trend H (1, 2)i vs n is fundamental K in the plots h ch observed hierarchical order on all stocks analysed (see Methods fora↵ects details). the We observe a positive = x e , (3) C. A Multivariate Dynamical Hierarchical Model i,t t 0.06 Nonetheless we mention report inmultivariate Figure 4 in SM) that without detrending series positive depe where ✏i,t = (✏t )i(and is a stationary Gaussian random variable, i.e. ✏t ⇠ Nthe (0, ⌃) with the ⌃ the covariance m2 etween0.03 the two variables up to n = 14, followed by some noisier0 flatbetween trend. The positive correlation 0.02 matrix and is is a volatility factor. from usual multivariate models, H (1, 2) and observed (for Di↵erently small n) in both TSE and HKSE data. i,t n i,t is not common to all stocks but depends explicitly on the hierarchical structure of the market. We suppose there is a volatility factor x common to (1, 2)i and n is also confirmed by performing a t-test on the correlation validated p-the We have detected samerandom positive dependence betweenlink hierarchical order and multifractality on specific where Kmwith are Bernoulli variables with pm between associated to the nodes am and along thet hierarchical In coefficient orderalso to the mechanism underlying the probabilities observed −0.01 sectors all explain stocks and then a latent hierarchical structure of risks am with m = 1,Q . . .multifractality ,N 1, associated withcorrelation the nodes of hierar the (i) (i) and on clusters found through DBHT clustering algorithm. We show in the top of Figure 3 plots K 0.04 3. All0.02 stocks with hierarchical order in the range [5, 14] (which accounts for 90% ofatree all stocks) exhibit therefore take the form = ✏whose xtmain , wherenovelty Ystochastic e .autocorrelated It istoworth remarking that the the dendrogram. The process x chosen as rai,tstationary process in time, with i . Returns i,t Yn,t log-normal t is introduce dynamical hierarchical model (DHM), respect standard multivariate n,t = with m2 0.015 multifractality indicator versus the hierarchical order computed on 1stocks to Financial and Ind autocovariance as a power law, i.e. Cov(x , in line belonging with a sweeping amount of studies (i) t xt+h ) ⇠ h properties increasing along with their depth in the hierarchy−0.02 of correlations. OnThe the other hand, the function hierarchical term Y introduces a single richer structure ofthe dependence, where the topology of{a the risk organisation plays [5] lies in the introduction of a decaying perturbation term on correlation matrix associated to its hierarchical str sectors. black dots are values stocks whereas the hierarchical red squares arei the average multifractal ind n,t on multi fractals in finance [21,for 22]. For the arbitrary stock i with path = , m 2 } we define the m i uration observed for orders larger than 14 suggests that the hierarchical ofreturns cross-correlations forstructure each order. We plot We model of also stock i asthe best fit on the dots (thick blue line). Both sets of stocks show a very well d 0.02 0.01 between the hierarchical order n and the multifractality H (1, 2), which is eviden nsible 0.01 for the multifractal properties of the stocks only up to−0.03 a certainpositive order. Letcorrelation us in particular 5 10 15 2 indicator 4 6 8 10 5 10 15 20 5 positive 10 note 15 20 trend recovered in both examples. Again, is found to be significant with p-value p = ri,tthe = ✏dependence n order n > 14 is too small to allowthe n n n i,t i,t , ber of stocks found with hierarchical any robust statistical conclusion, In Figure 3 we also report the trends observed on two of the largest clusters found through the DBHT. Th the reason why standard errors in Figure 2 are very large for n > 14. positive correlation between multifractality and hierarchical order is observed on the clusters best identifiable w m i m i 3 Model he hierarchical order is defined as the cardinality of e stock labeled by i, we have i = {1, 2, 4, 5, 8, 10}, red dots and ni = 6. i, i ni = card( i ). In the example reproduced in = {a1 , a2 , a4 , a5 , a8 , a10 }, i.e. the set of nodes ri,t = εi,tσ i,t σ i,t = xt ∏ e Km m∈γ i 0.25 !∆H (1, 2)" e of hierarchical structure. The path highlighted in red is i , while the thick red bullets are the nodes ch correspond to the risks stock i is exposed to. Note that the risk a1 is common to all stocks, while other s of stocks only. The dashed branches of the dendrogram indicate an arbitrary hierarchy. e conjecture that the hierarchical order ni can be actually viewed as a measure of the riskiness of of its positive dependence with multifractality. This entails that the cross-correlation properties of dataset are somehow entangled with the stylised facts displayed by the univariate time series. In erarchical structure of correlation provides likewise a snapshot of the hierarchy of risks in the market. ur knowledge, up to now no attempt to uncover this kind of underlying structure has been made in II. A. 0.2 0.15 RESULTS Cluster detection and sectors idered daily stock prices comprising the 342 most capitalised stocks continuously traded in the NYSE 01-1997 to 31-12-2012. Data have been provided by Bloomberg. The dataset includes stocks from et sectors, according to the Bloomberg classification. The taxonomy of the stocks in the respective in the Supplementary Material (SM), where we also report details on the clusters detected through g algorithm. We have chosen to perform the clustering through DBHT after having verified that it an other methods including the Single Linkage Cluster Analysis (SLCA) [33] in recovering a wellrchical structure: SLCA in fact tends to produce very large hubs of stocks that bias the correlation er. 0.1 0.05 2 3 4 5 n 6 7 8 9 Conclusions and Perspectives Complexity in the evolution in time of a variable Complexity in the dynamics of all variables Quantification of multi-scale temporal complexity - Empirical mode decomposition Noemi Nava Quantification of hierarchical dependency and causality - Kernel methods Anna Zaremba Information filtering through networks - Embedded graphs Guido Previde Massara Modeling risk propagation - Statistical mechanics approach Annika Wipprecht - Simulation and empirical study Satjaporn Tungsong Modeling financial processes with large fluctuations and non-linear dependency - Scaling laws Peter Divós Thank YOU! Si l’ordre satisfait la raison, le désordre fait les délices de l’imagination Paul Claudel