A new law of large numbers for single catastrophic risks.
problem Insurance risks from a single catastrophic event.
method Large diversification effect through optimal allocation to many reinsurers or investors.
result Derives a strong law of large numbers for insurance risks.
Study on diversification of α-stable risks, revealing limits to diversification due to tail dependence.
problem Diversification of α-stable risks with tail dependence. method Analysis of aggregated Value-at-Risk under different tail dependence structures.
result Limits to diversification are violated, especially for low tail index values and positive dependence.
The quantification of diversification benefits due to risk aggregation plays a prominent role in the (regulatory) capital management of large firms within the financial industry. However, the complexity of today's risk landscape makes a quantifiable reduction of risk concentration a challenging task. In the present pap…
Review of diversification models finds simple rules still best.
problem Testing new diversification models for out-of-sample performance.
method Tested sixteen strategies across six datasets.
result No new models consistently outperform simple diversification rules.
Oil is perceived as a good diversification tool for stock markets. To fully understand this potential, we propose a new empirical methodology that combines generalized autoregressive score copula functions with high frequency data and allows us to capture and forecast the conditional time-varying joint distribution of …
New methods show sparse portfolios offer no advantage over mean-variance in diversification.
problem Investment diversification and risk management with sparse portfolios.
method Developed and implemented a new estimation procedure for sparse second-order stochastic spanning using a greedy algorithm and Linear Programming.
result No benefit from expanding a sparse opportunity set beyond 45 assets; optimal sparse portfolio reduces tail risk.
Investment diversification increased during the financial crisis, but similarity between funds remains a systemic risk.
problem Systemic risk in mutual fund investments during the financial crisis.
method Investigated the bipartite network of US mutual fund portfolios and their assets, analyzed their evolution during the crisis, and introduced a simplified model of financial shock propagation.
result Large overlap between mutual fund portfolios is more likely than expected, indicating strong correlations and systemic risk.
The paper addresses portfolio diversification under model uncertainty using robust dynamic mean-variance approach.
problem Model uncertainty in portfolio diversification and its effects on optimal strategies.
method Develops a continuous time framework for dynamic multi-asset mean-variance portfolio selection under model uncertainty, considering ambiguity aversion in expected return rates and correlation matrix.
result Proves a separation principle for robust control problem, reducing optimal dynamic strategy determination to minimal risk premium computation.
We model the influence of sharing large exogeneous losses to the reinsurance market by a bipartite graph. Using Pareto-tailed claims and multivariate regular variation we obtain asymptotic results for the Value-at-Risk and the Conditional Tail Expectation. We show that the dependence on the network structure plays a fu…
Much of the analysis of economic growth has focused on the study of aggregate output. Here, we deviate from this tradition and look instead at the structure of output embodied in the network connecting countries to the products that they export.We characterize this network using four structural features: the negative r…
This study uses Tsallis entropy to analyze diversification and integration in Italian stock market companies.
problem Examining the industrial structure and market reactions of cross-shareholding networks.
method Developed Tsallis entropy approach to model diversification and integration using copulas.
result Entropy analysis reveals insights into market polarisation and fairness.
Paper models cloud outages for cyber insurance stress-testing.
problem Cyber insurance portfolios' vulnerability to simultaneous cloud outages.
method Modeling and calibrating cloud-outage scenarios, measuring diversification.
result Cloud-outage diversification can protect against accumulation risk.
Investigates how diversification preferences relate to risk attitudes.
problem Connecting diversification preferences to risk attitudes.
method Analyzes diversification preferences for various pairs of risks under different conditions.
result Diversification preferences for certain pairs of risks imply specific levels of risk aversion.
We present an extension of the Johansen-Ledoit-Sornette (JLS) model to include an additional pricing factor called the "Zipf factor", which describes the diversification risk of the stock market portfolio. Keeping all the dynamical characteristics of a bubble described in the JLS model, the new model provides additiona…
Study examines diversification of mid-mountain ski tourism.
problem Understanding transformations in ski mid-mountain territories.
method Applied regional diversification theory to French ski areas.
result Identified three steps in tourism diversification paths.
Specialization and diversification are two major strategies that complex systems might exploit. Given a fixed amount of resources, the question is whether to invest this in elements that respond in a correlated manner to external perturbations, or to build a diversified system with groups of elements that respond in a …
Diversification increases systemic risk, contrary to belief.
problem Systemic risk due to diversification at banks.
method Examined diversification's impact on joint default probability and systemic risk using VaR.
result Diversification reduces individual and systemic risk, contrary to common belief.
The study provides foundations for naive diversification, a preference for equal treatment of alternatives.
problem Understanding and mathematically grounding naive diversification preferences.
method Axiomatization of naive diversification as a preference for equality over inequality, and derivation of its relationship to classical diversification.
result Naive diversification is a preference for equality over inequality, and it is characterized by convex and permutation invariant preferences.
The paper proposes a new approach to portfolio selection that maximizes diversification and return.
problem Maximizing diversification and return in portfolio selection.
method A bi-objective model that maximizes a diversification measure and portfolio expected return.
result The return-diversification approach outperforms strategies based on diversification or classical risk-return approaches.
New method diversifies risk using complex numbers.
problem Minimizing portfolio risk under constraints.
method Complex valued principal component analysis in risk diversification.
result Outperforms conventional risk parity and diversification methods.
A new diversification measure DQ derived from risk measures addresses limitations of existing indices.
problem Limitations of existing diversification indices in capturing tail heaviness and common shocks.
method DQs are defined based on a parametric family of risk measures, satisfying six axioms of diversification.
result DQs can properly capture tail heaviness and common shocks, improving portfolio selection.
Paper introduces lexical ratio to measure portfolio diversification.
problem Traditional diversification metrics overlook non-numerical relationships.
method Uses textual data to capture diversification dimensions through entropy-based insights.
result Lexical ratio (LR) outperforms traditional metrics in optimizing portfolio returns.
The benefits of portfolio diversification is a central tenet implicit to modern financial theory and practice. Linked to diversification is the notion of breadth. Breadth is correctly thought of as the number of in- dependent bets available to an investor. Conventionally applications us- ing breadth frequently assume o…
The abstract discusses how diversification and securitization lead to information losses in financial risk optimization.
problem Information loss in financial risk optimization practices.
method Information theoretic concepts to quantify information losses in financial transformations and portfolios.
result Diversification and securitization increase information sensitivity, leading to maximal information losses when assets are uncorrelated.
One of the findings of the recent literature is that the 2008 financial crisis caused reduction in international diversification benefits. To fully understand the possible potential from diversification, we build an empirical model which combines generalised autoregressive score copula functions with high frequency dat…
Coherent diversification of tech fields correlates with higher labor productivity.
problem Understanding how firms' technological diversification impacts productivity.
method Analyzed patent data of 70k firms over 2004-2013, defined coherent diversification as network of related tech fields.
result Firms with coherent diversification structure outperform those with scattered diversification in labor productivity.
This paper challenges the conventional wisdom of trend-following by showing that the medium-term horizon adds little value once short- and long-term components are included.
problem The conventional wisdom that more horizons improve diversification and performance is challenged.
method A Bayesian optimization framework reallocates exposure dynamically across horizons, optimizing horizon-level weights at the asset level and applying sparsity and turnover control for dynamic allocation across assets.
result The medium-term horizon contributes little incremental performance or diversification once short- and long-term components are included.
Financial integration and diversification can lead to instability.
problem Understanding how financial network topology leads to instability.
method Analyzing the effects of market integration and diversification on financial network stability.
result Processes that stabilize financial systems can actually destabilize them.
Diversification improves profits for heavy-tailed investments.
problem Investment portfolios of Pareto-distributed returns.
method Stochastic dominance and majorization order.
result Diversification increases first-order stochastic dominance for heavy-tailed returns.
Investigates diversification quotient based on VaR and ES for portfolio models.
problem Quantifying diversification of portfolios using VaR and ES.
method Introduced and analyzed DQ based on VaR and ES for elliptical and MRV distributions.
result Explicit formulas and portfolio optimization problems for VaR and ES DQ are derived.
New framework optimizes portfolio diversification beyond mean-variance.
problem Optimizing portfolio diversification beyond classical methods.
method Introduces portfolio dimensionality, connects diversification to non-Gaussian returns, and develops global optimization algorithms.
result Maximizing portfolio dimensionality leads to highly non-trivial optimization problems with multiple local optima.
Diversification represents the idea of choosing variety over uniformity. Within the theory of choice, desirability of diversification is axiomatized as preference for a convex combination of choices that are equivalently ranked. This corresponds to the notion of risk aversion when one assumes the von-Neumann-Morgenster…
This paper improves the Diversification Quotient (DQ) for better risk management.
problem Improving portfolio diversification measurement.
method Empirical estimation of DQ using VaR and ES, with asymptotic properties verified.
result Empirical DQ estimators are more robust and have better asymptotic properties.
The paper explores tail diversification in financial markets using entropy and mutual information.
problem Tail diversification in financial time series.
method Statistical independence through differential entropy and mutual information, using moments as contrast functions.
result Tail covariance matrix is a key driver of tail diversification.
Investment diversification affects financial stability, depending on network connectivity.
problem Analyzing stability of financial networks with diversified portfolios.
method Random matrix dynamical model with portfolio rebalancing, considering heterogeneity and diversification effects.
result Stability/instability transition depends on the largest eigenvalue of the random matrix.
Analysis shows diversification of risks isn't always better.
problem The effectiveness of diversification in risk management.
method Examined individual risk characteristics and dependence relationships.
result Diversification is not always superior to non-diversification.
We present four methods of assessing the diversification potential within a stock market, two of these are based on principal component analysis. They were applied to the Australian stock exchange for the years 2000 to 2014 and all show a consistent picture. The potential for diversification declined almost monotonical…
Defines diversification as a binary relationship between financial portfolios.
problem Defines diversification in a new binary relationship for financial portfolios.
method Proposes a new definition of diversification based on convex linear combinations and second order stochastic dominance.
result The proposed definition coincides with second order stochastic dominance.
Analyzes re-ranking diversification algorithms based on function optimization.
problem Improving diversification in ranking systems.
method Examines re-ranking algorithms based on maximizing submodular/modular functions and their optimality in terms of total curvature.
result Adjusting hyperparameters can optimize relevance-diversity trade-offs.
The optimization of large portfolios displays an inherent instability to estimation error. This poses a fundamental problem, because solutions that are not stable under sample fluctuations may look optimal for a given sample, but are, in effect, very far from optimal with respect to the average risk. In this paper, we …
Diversification return is an incremental return earned by a rebalanced portfolio of assets. The diversification return of a rebalanced portfolio is often incorrectly ascribed to a reduction in variance. We argue that the underlying source of the diversification return is the rebalancing, which forces the investor to se…
Risk-only investment strategies have been growing in popularity as traditional in- vestment strategies have fallen short of return targets over the last decade. However, risk-based investors should be aware of four things. First, theoretical considerations and empirical studies show that apparently dictinct risk-based …
A new portfolio method using quantum mechanics improves risk diversification.
problem Improving risk-based portfolio construction methods for multi-asset portfolios.
method Schrödinger principal component analysis applied to extract common factors from asset fluctuations.
result The proposed method outperforms conventional risk parity and other risk diversification methods.
The study revisits portfolio diversification by relaxing assumptions for skewed, multi-regime, and leptokurtic asset returns.
problem Underestimation of risk in portfolio diversification due to assumptions that are inconsistent with real-world asset returns.
method Calibrated a Markov-modulated Levy process model to equity market data to demonstrate the merits of the approach.
result The calibrated models effectively match empirical moments and show the importance of relaxing assumptions in portfolio diversification.
Study on diversifying equity portfolios during financial crises and stability.
problem Determining the effectiveness of diversification strategies during financial crises and stability.
method Analysis of 20 years of US stock price data, including GFC and COVID-19 crashes, using eigenvalues, graph-theoretic diagnostics, and hierarchical clustering.
result During financial crises, diversification via sector-based portfolios is ineffective, while during stability, 30-40 stocks provide sufficient diversification.
Investing in cryptocurrencies can improve portfolio risk-return profile, especially with diversification strategies.
problem Investing in cryptocurrencies and evaluating their potential for portfolio allocation strategies.
method Investigated different types of investors, various portfolio construction rules, and incorporated liquidity constraints.
result Cryptocurrencies can improve the risk-return profile of portfolios, especially with diversification strategies.
This paper revisits mean-variance portfolio theory, addressing limitations in diversification models.
problem Current diversification models assume exchangeable asset returns and ignore risk-free assets.
method Analyzes diversification under full information about asset returns and risk, considering both risky and risk-free assets.
result The conventional wisdom of mean-variance portfolio theory is not universally valid, especially when asset returns are not exchangeable.
Optimizes portfolios with utility theory, diversification, and leverage.
problem Finding optimal portfolio allocation strategies.
method Utility theory, exponential and logarithmic utilities, compound probability distributions, maximum expected utility, generalized mean-variance.
result Enhanced portfolio allocation strategies with natural explanations.