Options and earnings announcements: an empirical study of volatility, trading volume, open interest and liquidity

In this paper we study the impact of earnings announcements on implied volatility, trading volume, open interest and spreads in the stock options market. We find that implied volatility increases before announcement days and drops afterwards. Also option trading volume is higher around announcement days. During the days before the announcement open interest tends to increase, while it returns to regular levels afterwards. Changes in the quoted spread largely respond to higher trading volume and changes in implied volatility. The effective spread increases on the event day and on the first two days following the earnings announcement.     

Determination of an order-up-to policy in the stochastic economic lot scheduling model

We consider a production–inventory problem with compound renewal item demand. The model consists of stockpoints, one for each item, controlled according to (R,S)-policies and one machine which replenishes them. The replenishment orders are produced with a fixed rate on the machine with significant setup times and costs, which are stochastic and sequence dependent. The time between the release and the production of the replenishment order is called the waiting time. We develop analytical approximations for the first two moments of this waiting time, the order-up-to levels and the average physical inventory levels for all stockpoints, given the target fill rates. These analytical approximations allows for a quick evaluation of the waiting time which is important when optimization of the system is considered.     

Minimal manipulability: Unanimity and nondictatorship

This paper is concerned with the number of profiles at which a nondictatorial social choice function is manipulable. For three or more alternatives the lower bound is found for unanimous social choice functions. In the case of three alternatives the lower bound is found for surjective social choice functions. In both cases all social choice functions reaching the lower bound are characterized for more than two agents. In the case of two agents the characterized social choice functions form a subset of the set of all social choice functions reaching the minimum.     

Estimating obsolescence risk from demand data to enhance inventory control—A case study

In this paper obsolescence of service parts is analyzed in a practical environment. Based on the analysis, we propose a method that can be used to estimate the risk of obsolescence of service parts, which is subsequently used to enhance inventory control for those parts. The method distinguishes groups of service parts. For these groups, the risk of obsolescence is estimated using the behavior of similar groups of service parts in the past. The method uses demand data as main information source, and can therefore be applied without the use of an expert's opinion. We will give numerical values for the risk of obsolescence obtained with the method, and the effects of these values on inventory control will be examined.     

Reallocation of an infinitely divisible good

Summary. We consider the problem of reallocating the total initial endowments of an infinitely divisible commodity among agents with single-peaked preferences. With the uniform reallocation rule we propose a solution which satisfies many appealing properties, describing the effect of population and endowment variations on the outcome. The central properties which are studied in this context are population monotonicity, bilateral consistency, (endowment) monotonicity and (endowment) strategy-proofness. Furthermore, the uniform reallocation rule is Pareto optimal and satisfies several equity conditions, e.g., equal-treatment and envy-freeness. We study the trade-off between properties concerning variation and properties concerning equity. Furthermore, we provide several characterizations of the uniform reallocation rule based on these properties. Received: August 29, 1995; revised version June 26, 1996     

Flexicurity – a European Approach to Labour Market Policy

Although linguistically somewhat strange, “flexicurity”, the combination of labour market flexibility and security for employees, has become a much praised cornerstone of European labour market policies. Obviously, in an environment with rapid technical progress and frequently changing market conditions, employers need to manage their labour force flexibly. In order to achieve this flexibility without creating an unbearable situation for employees, security is the second pillar of the concept. Security refers, however, to “employability” rather than safety from dismissal. As such, the concept looks like an innovative European way of consolidating economic and social interests, although some argue that much flexibility is gained while the security aspect is being neglected. The concept has been successfully adopted in some European countries, notably Denmark and the Netherlands. However, each country has to find its own concept of “flexicurity” using a distinct combination of instruments that fit the national institutional, social and civic context.