Some Cracks in the Empire of Chance (Flaws in the Foundations of Reliability)

Making quantified statements about the uncertainty associated with the lifelength of an item is one of the most fundamental tasks of reliability assessment. Most practitioners routinely do this using one of the several available statistical techniques. The purpose of this paper is two-fold. The first is to give the user an overview of the key tenets of two of the most commonly used parametric approaches. The second is to point out that these commonly used approaches involve strategies that are either ad hoc, or are in violation of some of the underlying tenets. A method that is devoid of logical flaws can be proposed, but this method is difficult to implement. The user must therefore resign to using that technique against which the fewest objections can be hurled.     

An integrated multi-model credit rating system for private firms

This paper presents a integrated credit risk modelling approach for private firms which fulfil 2001 Basel Accord requirements in the case of the adoption of the foundation approach. Our model comprises: (a) a bottom-up technique to initially assess the through-the-cycle one-year Probability of Default (PD) and (b) a top-down approach to refine and calibrate this historical PD in a forward-looking credit risk assessment based on next year’s economic outlook. We present findings from applying this model to a large sample of client firms of the Bank of Rome.     

IRB法下公司敞口组合的风险驱动因子计量研究

巴塞尔银行监管委员会针对防范信贷组合信用风险所需要的资本制定的内部评级法,通过风险驱动因子的变化来反映组合回报的变化,并根据风险权重函数,通过风险加权资产转化为与每一项信用风险敞口更准确匹配的资本要求.本文对违约概率、违约损失率、违约敞口、期限因素以及违约相关性等信贷组合信用风险的风险驱动因子的度量进行了综合研究.     

Why do companies transfer the trading compartment of their common stocks

We analyze the motives and determinants of voluntarily stock exchange section switching on the NYSE Euronext. By strategically deciding trading-section transfer when it is beneficial, managers expect to reduce their liquidity and invisibility costs, cost of capital, or their listing costs. We show that managers decide to change the trading compartment of their common stocks based on various factors including firm's size, liquidity level, debt ratio, and expected growth opportunities. Firms that move voluntarily from a less or non regulated compartments to a more regulated one are likely to have transferred to increase their credibility, improve their stocks’ liquidity, re-balance their leverage, and to finance their growth opportunities. Whereas those that move their common stocks toward a less-regulated compartments do it mainly for costs saving reasons.     

Combining multiple probability predictions using a simple logit model

This paper begins by presenting a simple model of the way in which experts estimate probabilities. The model is then used to construct a likelihood-based aggregation formula for combining multiple probability forecasts. The resulting aggregator has a simple analytical form that depends on a single, easily-interpretable parameter. This makes it computationally simple, attractive for further development, and robust against overfitting. Based on a large-scale dataset in which over 1300 experts tried to predict 69 geopolitical events, our aggregator is found to be superior to several widely-used aggregation algorithms.     

Forecasting the urban skyline with extreme value theory

The world’s urban population is expected to grow fifty percent by the year 2050 and exceed six billion. The major challenges confronting cities, such as sustainability, safety, and equality, will depend on the infrastructure developed to accommodate the increase. Urban planners have long debated the consequences of vertical expansion—the concentration of residents by constructing tall buildings—over horizontal expansion—the dispersal of residents by extending urban boundaries. Yet relatively little work has predicted the vertical expansion of cities and quantified the likelihood and therefore urgency of these consequences.We regard tall buildings as random exceedances over a threshold and use extreme value theory to forecast the skyscrapers that will dominate the urban skyline in 2050 if present trends continue. We predict forty-one thousand skyscrapers will surpass 150 meters and 40 floors, an increase of eight percent a year, far outpacing the expected urban population growth of two percent a year. The typical tall skyscraper will not be noticeably taller, and the tallest will likely exceed one thousand meters but not one mile. If a mile-high skyscraper is constructed, it will hold fewer occupants than many of the mile-highs currently designed. We predict roughly three-quarters the number of floors of the Mile-High Tower, two-thirds of Next Tokyo’s Sky Mile Tower, and half the floors of Frank Lloyd Wright’s The Illinois—three prominent plans for a mile-high skyscraper. However, the relationship between floor and height will vary considerably across cities.     

Effects of subject pool culture and institutional environment on corruption: Experimental evidence from Albania

This research uses experimental methods to investigate whether subject pool culture and institutional environment have an effect on participants’ corrupt behavior in the laboratory. While we find that subject pool culture does not affect the overall magnitude of corruption of laboratory participants, it does affect the likelihood of corruption and its distribution. Additionally, we find that the effect on corrupt behavior differs with the framing of the experiment’s instructions. Interestingly, in the context of a weak rule of law and high levels of corruption, loaded negative instructions positively affect corrupt behavior of firms and public officials. Previous research in the context of a country exhibiting a strong rule of law and low levels of corruption finds no framing effects. We also find that increasing the probability of detection significantly reduces corruption as measured by the amount of the bribes offered/accepted and the probability of offering/accepting a bribe. Finally, we find that individual risk preferences negatively affect the level of corrupt behavior.     

Disentangling acquisition experience: A multilevel analysis and future research agenda

Research interest in firms repeatedly involved in acquisitions has increased over the past decade. However, this increase has remained unmatched by efforts to integrate what is known, leaving the acquisition experience research field scattered, in turn hampering further theoretical and empirical progress. Taking a broad approach to experience, we review 106 empirical studies published in leading journals that focus on the effects of past acquisitions on subsequent ones. We discover three distinct but complementary ways in which research has dealt with experience. Moreover, research on acquisition experience has drawn conclusions on three important but insufficiently integrated levels of analysis. Our review delineates and systematises the current theoretical and empirical progress in acquisition experience research and outlines a future research agenda.     

随机数在随机事件与概率教学中的应用探索

本文对在随机事件与概率中的常见问题提出了一种新的借助于计算机实现的解决思路,即通过机器自动产生随机数后构建相应的数学模型,再通过编程计算得到最后结果。该方法既为概率论的教学带来了创新性思维,也为当前的教师提出了新的挑战。     

The roles of multiple channels in predicting website visits and purchases: Engagers versus closers

In today’s online environment, consumers and sellers interact through multiple channels such as email, search engines, banner ads, affiliate websites and comparison-shopping websites. In this paper, we investigate whether knowing the history of channels the consumer has used until a point of time is predictive of their future visit patterns and purchase conversions. We propose a model in which future visits and conversions are stochastically dependent on the channels a consumer used on their path up to a point. Salient features of our model are: (1) visits by consumers are allowed to be clustered, which enables separation of their visits into intra- and inter-session components, (2) interaction effects between channels where prior visits and conversions from channels impact future inter-session visits, intra-session visits and conversions through a latent variable reflecting the cumulative weighted inventory of prior visits, (3) each channel attracts inter-session and intra-session visits differently, (4) each channel has different association with conversion conditional on a customer’s arrival to the website through that channel, (5) each channel engages customers differently (i.e., keeps the customer alive for a next session or for a next visit within a session), (6) the channel from which there was an arrival in the previous session can have an enhanced ability to generate an arrival for the same channel in the current session (channel persistence), and (7) parsimonious specification for high dimensionality in a low-velocity, sparse-data environment. We estimate the model on easy-to-collect first-party data obtained from an online retailer selling a durable good and find that information on the identities of channels and incorporation of inter- and intra-session visits have significant predictive power for future visitation and conversion behavior. We find that some channels act as “closers” and others as “engagers”—consumers arriving through the former are more likely to make a purchase, while consumers arriving through the latter, even if they do not make a purchase, are more likely to visit again in the future or extend the current session. We also find that some channels engage customers more than others, and that there are interaction effects between the channels visited. Our estimates show that the effect of prior inventory of visits is different from the immediate prior visit, and that visit and purchase probabilities can increase or decrease based on the history of channels used. We discuss several managerial implications of the model including using the predictions of the model to aid in selecting customers for marketing actions and using the model to evaluate a policy change regarding the obscuring of channel information.