Risk Taking with Additive and Multiplicative Background Risks

We examine the effects of background risks on optimal portfolio choice. Examples of background risks include uncertain labor income, uncertainty about the terminal value of fixed assets such as housing and uncertainty about future tax liabilities. While some of these risks are additive and have been amply studied, others are multiplicative in nature and have received far less attention. The simultaneous effect of both additive and multiplicative risks has hitherto not received attention and can explain some paradoxical choice behavior. We rationalize such behavior and show how background risks might lead to seemingly U-shaped relative risk aversion for a representative investor.Derived risk aversion, Additive, multiplicative background risk

Multiplicative Background Risk

Although there has been much attention in recent years on the effects of additive background risks, the same is not true for its multiplicative counterpart. We consider random wealth of the multiplicative form xy, where x and y are statistically independent random variables. We assume that x is endogenous to the economic agent, but that y is an exogenous and nontradable background risk, which represents a type of market incompleteness. Our main focus is on how the presence of the multiplicative background risk y affects risk-taking behavior for decisions on the choice of x. We characterize conditions on preferences that lead to more cautious behavior.multiplicative risks, background risk, incomplete markets, standard risk aversion, affiliated utility function, multiplicative risk vulnerability

Multiplicative background risk

We consider random wealth of the multiplicative form xy, where x and y are statistically independent random variables. We assume that x is endogenous to the economic agent, but that y is an exogenous and uninsurable background risk. Our main focus is on how the randomness of y affects risk-taking behavior for decisions on the choice of x. We characterize conditions on preferences that lead to more cautious behavior. We also develop the concept of the affiliated utility function, which we define as the composition of the underlying utility function and the exponential function. This allows us to adapt several results for additive background risk to the multiplicative case. -- Wir betrachten den zufälligen Reichtum der multiplikativen Form xy, wo x und y statistisch unabhängige Zufallsvariablen sind. Wir nehmen an, daß x endogen für den ökonomischen Agenten ist, aber daß y ein exogenes und nicht versicherbares Hintergrundrisiko ist. Unser Hauptaugenmerk liegt darauf, wie die Zufälligkeit von y das Risikoverhalten bei Entscheidungen für x beeinflußt. Wir charakterisieren die Bedingungen der Präferenzen, die zu einem vorsichtigeren Verhalten führen. Wir entwickeln auch ein Konzept der „affiliated“ Nutzenfunktion, die eine Zusammensetzung der ursprünglichen Nutzenfunktion und der Exponentialfunktion ist. Dies erlaubt es uns, mehrere Ergebnisse für additive Hintergrundrisiken auf den multiplikativen Fall anzupassen.background risk,standard risk aversion,affiliated utility function

Quantum-classical transition and quantum activation of ratchet currents in the parameter space

The quantum ratchet current is studied in the parameter space of the dissipative kicked rotor model coupled to a zero temperature quantum environment. We show that vacuum fluctuations blur the generic isoperiodic stable structures found in the classical case. Such structures tend to survive when a measure of statistical dependence between the quantum and classical currents are displayed in the parameter space. In addition, we show that quantum fluctuations can be used to overcome transport barriers in the phase space. Related quantum ratchet current activation regions are spotted in the parameter space. Results are discussed {based on quantum, semiclassical and classical calculations. While the semiclassical dynamics involves vacuum fluctuations, the classical map is driven by thermal noise.Comment: 6 pages, 3 figure

Copyright and cultural work: an exploration

This article first discusses the contemporary debate on cultural “creativity” and the economy. Second, it considers the current state of UK copyright law and how it relates to cultural work. Third, based on empirical research on British dancers and musicians, an analysis of precarious cultural work is presented. A major focus is how those who follow their art by way of “portfolio” work handle their rights in ways that diverge significantly from the current simplistic assumptions of law and cultural policy. Our conclusions underline the distance between present top-down conceptions of what drives production in the cultural field and the actual practice of dancers and musicians

Multiplicative background risk

"We consider random wealth of the multiplicative form xy, where x and y are statistically independent random variables. We assume that x is endogenous to the economic agent, but that y is an exogenous and uninsurable background risk. Our main focus is on how the randomness of y affects risk-taking behavior for decisions on the choice of x. We characterize conditions on preferences that lead to more cautious behavior. We also develop the concept of the affiliated utility function, which we define as the composition of the underlying utility function and the exponential function. This allows us to adapt several results for additive background risk to the multiplicative case." (author's abstract)"Die Autoren betrachten den zufälligen Reichtum der multiplikativen Form xy, wo x und y statistisch unabhängige Zufallsvariablen sind. Sie nehmen an, das x endogen für den ökonomischen Agenten ist, aber das y ein exogenes und nicht versicherbares Hintergrundrisiko ist. Das Hauptaugenmerk liegt darauf, wie die Zufälligkeit von y das Risikoverhalten bei Entscheidungen für x beeinflusst. Die Autoren charakterisieren die Bedingungen der Präferenzen, die zu einem vorsichtigeren Verhalten führen. Sie entwickeln auch ein Konzept der 'affiliated' Nutzenfunktion, die eine Zusammensetzung der ursprünglichen Nutzenfunktion und der Exponentialfunktion ist. Dies erlaubt es, mehrere Ergebnisse für additive Hintergrundrisiken auf den multiplikativen Fall anzupassen." (Autorenreferat

Field Dependence of the Superconducting Basal Plane Anisotropy of TmNi2B2C

The superconductor TmNi2B2C possesses a significant four-fold basal plane anisotropy, leading to a square Vortex Lattice (VL) at intermediate fields. However, unlike other members of the borocarbide superconductors, the anisotropy in TmNi2B2C appears to decrease with increasing field, evident by a reentrance of the square VL phase. We have used Small Angle Neutron Scattering measurements of the VL to study the field dependence of the anisotropy. Our results provide a direct, quantitative measurement of the decreasing anisotropy. We attribute this reduction of the basal plane anisotropy to the strong Pauli paramagnetic effects observed in TmNi2B2C and the resulting expansion of vortex cores near Hc2.Comment: 8 pages, 6 figures, 1 tabl