Alternative to beta coefficients in the context of diffusions

We develop an alternative to the beta coefficient of the CAPM theory. We show the link between this notion and the Wiener chaos expansion of the underlying processes. In the setting of Markov diffusions, we define the drift-neutral beta, which is the quantity of benchmark such that the resulting portfolio is immune to an infinitesimal change of drift on the Brownian motion driving the benchmark. Our approach yields a coefficient which in many practical cases depends on the initial values of both the portfolio and its benchmark. It can also be used to take into account extreme risks and not only the variance. We study several classical diffusion processes and give a full analysis in the case of Jacobi processes. Examples with credit indices show the efficiency of the method in hedging a portfolio.     

Der deutsche Bankensektor

Although Germany’s banking sector has experienced a wave of consolidation, especially since the financial crisis, the country is still home to a high number of banking institutions. When domestic economic activity was sluggish in the mid-2000s, German banks searched for sources of income abroad; some of them have massively invested in structured products. As a consequence, the financial crisis of 2007–2009 has hit German banks harder than those from other eurozone countries. The European Commission has played a key role in restructuring the sector, asking in particular that banks which have received state aid strongly reduce their balance sheets — and ordering the liquidation of one of them. Since 2010 the German banking sector has returned to the profit zone and appears more robust thanks to an increase of equity and a reduction of balance sheets. The leverage ratio remains nevertheless significant, profitability remains low in a context of strong competition on the domestic market, and some banks find themselves deeply affected by the crisis of the shipping sector.     

A comment on “School choice: An experimental study” [J. Econ. Theory 127 (1) (2006) 202-231]

We show that one of the main results in Chen and Sönmez (2006, 2008) [6] and [7] does no longer hold when the number of recombinations is sufficiently increased to obtain reliable conclusions. No school choice mechanism is significantly superior in terms of efficiency.     

Payments and liquidity under adverse selection

Informational asymmetries regarding the future value of assets affect their role in exchange. I construct a random-matching economy composed of two assets: a risk-free bond and a Lucas tree whose terminal value is privately known to its holder. No restrictions are imposed on payment arrangements. The main finding supports a pecking-order theory of payments: Agents use their risk-free bonds first in order to finance their spending shocks, and they use their information-sensitive assets only if their holdings of bonds are depleted. The theory has implications for the optimal provision of risk-free bonds, the structure of asset returns, and liquidity.     

Reviewing South Africa's marketing and trade policies for genetically modified products

South Africa is unique in that it has commercialised genetically modified (GM) crops and has a functional biosafety system, which allows for trade in both GM and non-GM crops, despite being surrounded by countries banning the use of GM products. This paper analyses the past achievements and evolving changes in marketing and trade policies for GM products in South Africa. A quantitative analysis of South Africa's GM imports and exports demonstrates the success of South Africa's flexible regulatory system. Yet a review of recent reforms indicates a trend towards more rigid trade and marketing regulations of GM products. This paper suggests five policy recommendations to improve rather than rigidify regulations and allow South Africa to adapt to global changes, manage risks and take advantage of potentially promising new GM technologies.     

Multi-subject stochastic blockmodels with mixed effects for adaptive analysis of individual differences in human brain network cluster structure

Recently, there has been a renewed interest in the class of stochastic blockmodels (SBM) and their applications to multi-subject brain networks. In our most recent work, we have considered an extension of the classical SBM, termed heterogeneous SBM (Het-SBM), that models subject variability in the cluster-connectivity profiles through the addition of a logistic regression model with subject-specific covariates on the level of each block. Although this model has proved to be useful in both the clustering and inference aspects of multi-subject brain network data, including fleshing out differences in connectivity between patients and controls, it does not account for dependencies that may exist within subjects. To overcome this limitation, we propose an extension of Het-SBM, termed Het-Mixed-SBM, in which we model the within-subject dependencies by adding subject- and block-level random intercepts in the embedded logistic regression model. Using synthetic data, we investigate the accuracy of the partitions estimated by our proposed model as well as the validity of inference procedures based on the Wald and permutation tests. Finally, we illustrate the model by analyzing the resting-state fMRI networks of 99 healthy volunteers from the Human Connectome Project (HCP) using covariates like age, gender, and IQ to explain the clustering patterns observed in the data.     

Gamson's Law versus non-cooperative bargaining theory

We compare Gamson's Law, a popular empirical model of legislative bargaining, with two non-cooperative bargaining models in three players divide the dollar games in which no player has enough votes to form a winning coalition on their own. Both of the game theoretic models better organize the comparative static data resulting from changes in nominal bargaining power than does Gamson's Law. We also identify deviations from the point predictions of the non-cooperative bargaining models. Namely, proposer power is not nearly as strong as predicted under the Baron–Ferejohn model, and a significant number of bargaining rounds tend to take more than two steps under demand bargaining and more than one stage under Baron–Ferejohn, counter to the models' predictions. Regressions using the experimental data provide results similar to the field data, but fail to do so once one accounts for predictions regarding coalition composition under Gamson's Law.     

Window Double Barrier Options

This paper examines a path-dependent contingent claim called the window double barrier option, including standard but also more exotic features such as combinations of single and double barriers. Price properties and hedging issues are discussed, as well as financial applications.Explicit formulae are provided, along with simple techniques for theirimplementation. Numerical results show that they compare very favourablywith alternative pricing approaches in terms of accuracy and efficiency.