Reformulating Environmentally Constrained Traffic Equilibrium via a Smooth Gap Function

Various government laws have recently been enacted to alleviate the environmental deterioration of transportation systems. Environmental constraint is a valid means to explicitly reflect various environmental protection requirements imposed by the government. In this paper, we examine the environmentally constrained traffic equilibrium problem (EC-TEP), which is a fundamental tool for modeling and evaluating environmental protection requirements. Specifically, we provide an equivalent reformulation for the EC-TEP. The proposed reformulation adapts the concept of gap function to simultaneously reformulate the nonlinear complementarity conditions associated with the generalized user equilibrium conditions, environmental constraints, and conservation constraints as an equivalent unconstrained optimization problem. This gap function reformulation has two desirable features: (1) it can handle a general environmental constraint structure (linear or nonlinear; link-based or area-based) and a general link and route cost structure, enhancing the modeling adaptability and flexibility; (2) it is smooth and unconstrained, permitting a number of existing efficient algorithms for its solution. A gradient-based solution algorithm with a self-regulated averaging stepsize scheme is customized to solve the reformulated unconstrained optimization problem. Numerical examples are also provided to demonstrate the modeling flexibility of the proposed EC-TEP reformulation.     

Local competition, entry, and agglomeration

This paper analyzes competition between two spatially differentiated multi-product retailers who encounter entry from a low-cost discounter. We assess how entry affects the pricing of the incumbent stores and the role played by the location of the entrant. Our primary objective is to identify how traditional retailers respond to new forms of low-cost retailing. Results show that post entry, the prices for some products are higher than the pre entry. However, which product prices increase depends on the incumbent’s location. Contrary to conventional wisdom, we find that the store closer to the entrant is better off compared to the incumbent located further away. We empirically demonstrate the main workings of our theory using sales data from several grocery stores that saw entry by discount stores in their trading areas.     

Comparative effectiveness of standard endotracheal tubes vs. endotracheal tubes with continuous subglottic suctioning on ventilator-associated pneumonia rates

Ventilator-associated pneumonia (VAP) accounts for the majority of nosocomial pneumonias, which may increase intensive care and prolonged hospital stays. Endotracheal tubes allowing continuous subglottic suctioning may reduce VAP; however, they are more expensive than standard endotracheal tubes not allowing continuous suctioning. he objective of this study was to measure the comparative costs associated with continuous subglottic suctioning endotracheal tubes (CSS-ETT) versus standard endotracheal tubes (S-ETT) among intubated patients and whether cost differential is offset by the occurrence of VAP in patients receiving either type of intubation. A retrospective chart review was conducted for 154 intubated adult patients (77 = S-ETT; 77 = CSS-ETT). The S-ETT group had one case of VAP; the CSS-ETT group had none. The mean total hospital charges were higher for the S-ETT group ($103,600; CSS-ETT= $88,500) (p = 0.3). Although the average number of intubation days and ICU days were greater for the CSS-ETT group, there were no cases of VAP compared to the S-ETT group. ased upon the one S-ETT VAP case and the VAP attributable costs, it is cost effective to use the CSS-ETT.     

Asymmetric information without common priors: an indirect evolutionary analysis of quantity competition

The common prior assumption justifies private beliefs as posterior probabilities when updating a common prior based on individual information. We dispose of the common prior assumption for a homogeneous oligopoly market with uncertain costs and firms entertaining arbitrary priors about other firms’ cost-type. We show that true prior beliefs can not be evolutionarily stable when truly expected profit measures (reproductive) success.     

Asset prices in a Huggett economy

This paper explores asset pricing in economies where there is no direct insurance against idiosyncratic risks but other assets can be used for self-insurance, subject to exogenously-imposed borrowing limits. We analyze an endowment economy, based on Huggett (1993) [11], both with and without aggregate risk. Our main innovation is that we obtain full analytical tractability by studying the case with “maximally tight” borrowing constraints. We illustrate by looking at riskless bonds, equity, and the term structure of interest rates, and we show that the model can reproduce many features of observed asset prices when idiosyncratic risks are quantitatively reasonable.     

The Assimilative and Contrastive Effects of Word-of-Mouth Volume: An Experimental Examination of Online Consumer Ratings

The popularity of online rate-and-review websites has increased the importance of word-of-mouth (WOM) volume (number of ratings) yet the retail literature has not paid adequate attention to understanding its impact. This paper highlights WOM volume as a high-scope, decision-making cue upon which the influence of other WOM-relevant characteristics on a WOM message's persuability depends. We begin, via a pretest, by demonstrating the intuitive expectation that high volume, relative to low volume, accentuates or assimilates perceptions of positivity or negativity of WOM targets. Then, through two experimental studies, we show that depending upon how high volume interacts with WOM consensus and consumer decision precommitment, it can contrast preference away from the valence of a target also. In our third and final experimental study, we demonstrate that consumers differ in their susceptibility to the influence of high volume. Those with a higher desire to be different from others, compared to those with a higher desire to be similar, are resistant to high volume's assimilative sway and do not show the valence-accentuating effects demonstrated in the pretest. Retail managers and researchers should find these insights about the different roles of WOM volume beneficial.