Penalized h-likelihood approach for variable selection in AFT random-effect models

Survival models allowing for random effects (e.g., frailty models) have been widely used for analyzing clustered time-to-event data. Accelerated failure time (AFT) models with random effects are useful alternatives to frailty models. Because survival times are directly modeled, interpretation of the fixed and random effects is straightforward. Moreover, the fixed effect estimates are robust against various violations of the assumed model. In this paper, we propose a penalized h-likelihood (HL) procedure for variable selection of fixed effects in the AFT random-effect models. For the purpose of variable selection, we consider three penalty functions, namely, least absolute shrinkage and selection operator (LASSO), smoothly clipped absolute deviation (SCAD), and HL. We demonstrate via simulation studies that the proposed variable selection procedure is robust against the misspecification of the assumed model. The proposed method is illustrated using data from a bladder cancer clinical trial.     

When Does a Platform Create Value by Limiting Choice?

We present a theory for why it might be rational for a platform to limit the number of applications available on it. Our model is based on the observation that even if users prefer application variety, applications often also exhibit direct network effects. When there are direct network effects, users prefer to consume the same applications to benefit from consumption complementarities. We show that the combination of preference for variety and consumption complementarities gives rise to (i) a commons problem (to better satisfy their individual preference for variety, users have an incentive to consume more applications than the number that maximizes joint utility); (ii) an equilibrium selection problem (consumption complementarities often lead to multiple equilibria, which result in different utility levels for the users); and (iii) a coordination problem (lacking perfect foresight, it is unlikely that users will end up buying the same set of applications). The analysis shows that the platform can resolve these problems and create value by limiting the number of applications available. By limiting choice, the platform may create new equilibria (including the allocation that maximizes users' utility); eliminate equilibria that give lower utility to the users; and reduce the severity of the coordination problem faced by users.     

Valuation effects with transitory and trend productivity shocks

Changes in asset prices of a country's foreign assets and liabilities (“valuation effects”) are commonly thought of as stabilizing: they counteract current account movements and mitigate the impact of the current account on the country's net foreign asset (NFA) position. This paper shows that whether valuation effects are stabilizing or not depends critically on the nature of the underlying productivity shocks. In response to transitory shocks, valuation effects are stabilizing; but in response to trend shocks, such effects amplify the impact of the current account on NFA position. These contrasting effects arise because optimally smoothing consumers respond differently to a transitory shock than to a trend shock to income. This theoretical result finds empirical support with G7 countries' data, and is illustrated by the pattern of external imbalances between the U.S. and other G7 countries since the 1990s.     

The effect of consumers' involvement and innovativeness on the utilization of fashion wardrobe

This study proposed wardrobe utilization as a means of explaining consumer clothing use behaviour, and aimed to explore its relationship with other antecedent variables. We posit that use innovativeness functions as an antecedent of wardrobe utilization within a model comprised of fashion‐related variables, such as fashion innovativeness and fashion involvement. An empirical study was conducted to test this relationship with 211 adult women between the ages of 20 and 40 years. In order to calculate wardrobe utilization, the number of clothing items worn by each respondent was divided by the total number of clothes that the respective respondent owns. The findings of this study revealed a measureable effect of use innovativeness on wardrobe utilization and apparel purchase behaviour. In addition, fashion innovativeness and fashion involvement was shown to affect use innovativeness; however, the two variables did not have a significant impact on influencing wardrobe utilization. These results showed that use innovativeness plays a role of the full mediator variable in the path from fashion involvement and fashion innovativeness to wardrobe utilization. These also indicated that people who are very innovative in their use of fashion are likely to broadly utilize their respective wardrobes. Finally, the impact of purchase behaviour on wardrobe utilization was dismissed, as purchase behaviour and use behaviour were found to be clearly distinguished from one another. Clothing utilization is related to the life cycle of clothes including their purchase, usage and disposal. And in better understanding clothing utilization, the needless waste of clothing would be reduced and would encourage better management of clothes after their purchase. In the context of the product life cycle, this study of clothing use behaviour can assist in building a more sustainable environment for the textile and fashion industry.     

On the rationality of Korea's stock market: was the recent Korean financial crisis due to fundamental factors?

This paper examines whether the recent financial crisis in Korea was due to fundamental factors. To address this issue, we identify various components of Korea's stock market prices (KOSPI) and examine their responses to different types of shocks. Given the stationary behavior of KOSPI dividends, we relate stock price directly to earnings by deriving and using a log-linear model of the spread between price and earnings with a time-varying discount factor. Therefore, stock-price movements are explained by earnings (numerator component), time-varying discount factors (denominator component), and non-fundamental factors. Although we find evidence of substantial non-fundamental components in Korea's stock market prices, the sudden decline in Korea's stock market prices during the 1997 financial crisis was primarily due to fundamental components, in particular, the numerator component (e.g. earnings) combined with the denominator component (i.e. time-varying discount factor) rather than non-fundamental factors.     

Auctions for conservation contracts: an empirical examination of Victoria's BushTender trial

The present paper proposes that markets for nature conservation on private land are missing because of the problem of asymmetric information. An auction of conservation contracts was designed to reveal hidden information needed to facilitate meaningful transactions between landholders and government. The present paper describes the key elements of auction and contract design employed and the results obtained from a pilot auction of conservation contracts run in two regions of Victoria. The pilot demonstrated that it was possible to create at least the supply side of a market for nature conservation and in conjunction with a defined budget, prices were discovered and resources allocated through contracts with landholders. The present paper compares a discriminative price auction with a hypothetical fixed-price scheme showing that an auction could offer large cost savings to governments interested in nature conservation on private land. The paper identifies some important design problems that would need to be solved before auctions could be applied more broadly including: multiple complementary outcomes, reserve prices, sequential auction design and contract design. Nevertheless, the paper does show that auctioning conservation contracts for environmental outcomes is an important new policy mechanism that deserves closer examination.     

One Country,Two Prices? A Study of the Deflationary Effect of Price Convergence on Hong Kong*

Consumer prices in Hong Kong at the time of writing have declined by 15 percent from the peak recorded in 1998. We investigate the deflationary impact on Hong Kong of price convergence with the Mainland China, using 1990–2001 annual data on commodity prices in the former and in major cities of the latter. We find evidence of price convergence between the two economies over the past decade. Furthermore, price convergence is estimated to have accounted for one‐fifth of the deflation in Hong Kong. The results suggest that a significant portion of the deflation in Hong Kong is attributable to a process of structural adjustment due to growing economic integration with the Mainland.     

Modelling the emergence of the interbank networks

Interbank contagion has become a buzzword in the aftermath of the financial crisis that led to a series of shocks to the interbank market and to periods of pronounced market disruptions. However, little is known about how interbank networks are formed and about their sensitivity to changes in key bank parameters (for example, induced by common exogenous shocks or by regulatory initiatives). This paper aims to shed light on these issues by modelling endogenously the formation of interbank networks, which in turn allows for checking the sensitivity of interbank network structures and hence, their underlying contagion risk to changes in market-driven parameters as well as to changes in regulatory measures such as large exposures limits. The sequential network formation mechanism presented in the paper is based on a portfolio optimization model, whereby banks allocate their interbank exposures while balancing the return and risk of counterparty default risk and the placements are accepted taking into account funding diversification benefits. The model offers some interesting insights into how key parameters may affect interbank network structures and can be a valuable tool for analysing the impact of various regulatory policy measures relating to banks’ incentives to operate in the interbank market.     

The Evolution of Expectations of and Attitudes Toward Online Travel Agencies Over Time

The basic premise of this research is that customer satisfaction with online travel agencies (OTAs) is dynamic in nature. In this context, it still remains unclear what role satisfaction plays in affecting expectations and attitudes toward an online travel agent over time. The study thus utilizes longitudinal data from 353 customers of OTAs to test temporal and carryover effects pertaining to satisfaction. Results indicate that the temporal effect of the expectations–attitudes linkage decreases over time. Carryover effects suggest that customers integrate both pre- and post-travel assessments of expectations and attitudes when evaluating satisfaction.     

A mathematical model for multi-name credit based on community flocking

We present a new mathematical model for multi-name credit that employs stochastic flocking. Flocking mechanisms have been used in a variety of models of biological, sociological and physical aggregation phenomena. As a direct application of a flocking mechanism, we introduce a credit risk model based on community flocking for a credit worthiness index. Correlations between different credit worthiness indices are explained in terms of communication rates and coupling strengths from the flocking system. Based on the flocking model, we compute credit curves for individual names and default time distributions. We also apply the proposed model to the pricing of credit derivatives such as credit default swaps and collateralized debt obligations.