Improving the absorptive capacity through unlearning context: an empirical investigation in hospital-in-the-home units

The Spanish healthcare system has undergone important changes, particularly in the development of new homecare services. In practice, however, results have been mixed. Some homecare services have been successful, but implementation failures are common and the intended patients are frequently reluctant to use the homecare services. A possible explanation for efficiency and effectiveness gaps of services provided by hospital-in-the-home units (HHUs) may relate to the advantages and disadvantages of the knowledge processes that these units highlight as a result of their different structural properties. This study examines the impact of an unlearning (forgetting) context on the HHU's ability to challenge basic beliefs and to implement processes that are explicitly or tacitly helpful in the reception of new ideas (absorptive capacity). These relationships are examined through an empirical investigation of 54 doctors and 62 nurses belonging to 44 HHUs. The results show that the unlearning context plays a key role in managing the tension between potential absorptive capacity and realized absorptive capacity.     

Esscher transforms and the minimal entropy martingale measure for exponential Lévy models

In this paper we offer a systematic survey and comparison of the Esscher martingale transform for linear processes, the Esscher martingale transform for exponential processes, and the minimal entropy martingale measure for exponential Lévy models, and present some new results in order to give a complete characterization of those classes of measures. We illustrate the results with several concrete examples in detail.     

A new microstructure noise index

We introduce a new microstructure noise index for financial data. This index, the computation of which is based on the p-variations of the considered asset or rate at different time scales, can be interpreted in terms of Besov smoothness spaces. We study the behavior of our new index using empirical data. It gives rise to phenomena that a classical signature plot is unable to detect. In particular, with our data set, it enables us to separate the sampling frequencies into three zones: no microstructure noise for low frequencies, increasing microstructure noise from low to high frequencies, and some kind of additional regularity on the finest scales. We then investigate the index from a theoretical point of view, under various contexts of microstructure noise, trying to reproduce the facts observed on the data. We show that this can be partially done using models involving additive correlated errors or rounding error. Accurate reproduction seems to require either both kinds of error together or some unusual form of rounding error.     

Skewness premium with Lévy processes

We study the skewness premium (SK) introduced by Bates [J. Finance, 1991, 46(3), 1009–1044] in a general context using Lévy processes. Under a symmetry condition, Fajardo and Mordecki [Quant. Finance, 2006, 6(3), 219–227] obtained that SK is given by Bates' x% rule. In this paper, we study SK in the absence of that symmetry condition. More exactly, we derive sufficient conditions for the excess of SK to be positive or negative, in terms of the characteristic triplet of the Lévy process under a risk-neutral measure.     

The price impact of order book events: market orders,limit orders and cancellations

While the long-ranged correlation of market orders and their impact on prices has been relatively well studied in the literature, the corresponding studies of limit orders and cancellations are scarce. We provide here an empirical study of the cross-correlation between all these different events, and their respective impact on future price changes. We define and extract from the data the ‘bare’ impact these events would have if they were to happen in isolation. For large tick stocks, we show that a model where the bare impact of all events is permanent and non-fluctuating is in good agreement with the data. For small tick stocks, however, bare impacts must contain a history-dependent part, reflecting the internal fluctuations of the order book. We show that this effect can be accurately described by an autoregressive model of the past order flow. This framework allows us to decompose the impact of an event into three parts: an instantaneous jump component, the modification of the future rates of the different events, and the modification of the jump sizes of future events. We compare in detail the present formalism with the temporary impact model that was proposed earlier to describe the impact of market orders when other types of events are not observed. Finally, we extend the model to describe the dynamics of the bid–ask spread.     

Multiplicative noise,fast convolution and pricing

In this work we detail the application of a fast convolution algorithm to compute high-dimensional integrals in the context of multiplicative noise stochastic processes. The algorithm provides a numerical solution to the problem of characterizing conditional probability density functions at arbitrary times, and we apply it successfully to quadratic and piecewise linear diffusion processes. The ability to reproduce statistical features of financial return time series, such as thickness of the tails and scaling properties, makes these processes appealing for option pricing. Since exact analytical results are lacking, we exploit the fast convolution as a numerical method alternative to Monte Carlo simulation both in the objective and risk-neutral settings. In numerical sections we document how fast convolution outperforms Monte Carlo both in speed and efficiency terms.     

基于跳跃扩散过程的保险资金最优投资模型研究

保险公司的盈余为跳跃扩散过程,保险人投资于债券和股票,且股票的价格服从跳跃扩散过程的最优投资组合。在均值-方差准则下通过随机最优控制方法,建立并求解保险资金投资模型的HJB方程,获得了保险资金最优投资模型和有效边界的闭式解,并进行了数值模拟。结果显示,投资于风险证券的资金量与初始资本金并不是简单的正比例关系。     

Drivers of diffusion of consumer products: empirical evidence from the digital audio player market

We empirically study the factors affecting the timing of adoption of a consumer technology. We account for four possible effects (epidemic, probit, stock, and order effect) in relation to the diffusion of portable digital audio players (DAPs) using an original dataset of several hundred potential adopters from eight European countries and Japan. Our findings suggest that each one of these effects, which are often incorporated into competing models of diffusion, contribute to explain the diffusion of DAPs. Thus while researches informed by a specific approach to the study of innovation diffusion could lead to important results, they also run the risk of accounting for only a part of the phenomenon. This consideration highlights the quest for a more comprehensive approach to diffusion studies.     

Iterative Project Processes Within Temporary Multi‐Organizations in Construction: The Self‐, Eco‐, Re‐Organizing Projects

Theory‐based studies claim that informal processes interfere with the formal mechanisms and structures of projects in the construction sector. These processes structure and transform multi‐organizations. This four‐year case study reveals empirical evidence about how processes effectively evolve over time and affect formal mechanisms and structures. The results show: (1) the significant differences between what is planned and what actually unfolds in project processes; (2) how iterative processes overshadow linear ones; (3) how informality and “iterativity” eventually end up as self‐, eco‐, and re‐organizing projects and organizations, confirming that projects (re)create the very processes and structures that initiate them.     

Lévy过程驱动的随机LQ控制在均值-方差投资组合中的应用

文章研究了风险资产价格由Lévy过程和与之独立的多维Brown运动共同驱动的连续时间均值-方差型投资组合选择问题,Lévy过程是由与之相关的Teugles鞅描述。为了求解该问题,首先讨论了由Lévy过程和多维Brown运动共同驱动的非齐次随机系统的线性二次控制问题。借助配方法得到了一个新的随机Riccati方程,若此方程有解,就可以得到系统的最优反馈控制。然后将该理论结果用于求解均值-方差型投资组合问题,在自融资的条件下,得到了最优证券组合的显式表达。最后通过数值算例对比分析有Lévy过程和无Lévy过程情形下投资者的最优投资策略和有效前沿,发现Lévy过程的存在增加了投资者的投资风险,投资者应正确视之。