Columbia Business School Research

Observers viewed random-dot optical flow displays that simulated self-motion on a circular path and judged whether they would pass to the right or left of a target at 16 m. Two dots in 2 frames are theoretically sufficient to specify circular heading if the orientation of the rotation axis is known. Heading accuracies were better than 1.5° with a ground surface, wall surface, and 3-dimensional cloud of dots and were constant over densities down to 2 dots, consistent with the theory.

This article examines the use of share repurchase as a takeover deterrent. The main result is that in the presence of an upward-sloping supply curve for shares, the takeover cost to the acquirer can be greater if the target firm distributes cash through share repurchase than if it chooses either to pay a cash dividend or to do nothing. Because shareholders willing to tender the distribution of remaining shareholders toward a more expensive pool. Examining the equilibrium behavior of all players in a stylized takeover game, conditions exist under which repurchase deters takeover.

The nature of supply curves in corporate equity are examined. Until recently, there has been little direct empirical assessment of their elasticity. At issue is whether or not the supposition of shareholder homogeneity of valuations represents a good approximation to actual markets. In Bagwell (1990), supply curves documented in Dutch auction repurchases have a distinct upward slope. Shleifer (1990) also provides evidence of an upward-sloping supply curve.

We examine the effects of nonstationarity on the performance of multiserver queueing systems withe exponential service times and sinusoidal Poisson input streams. Our primary objective is to determine when and how a stationary model may be used as an approximation for a nonstationary system. We focus on a particular quesion: How nonstationary can an arrival process be before a simple stationary approximation fails? Our analysis reveals that stationary models can seriously underestimate delays when the actual system is only modestly nonstationary.

We establish strong consistency (i.e., almost sure convergence) of infinitesimal perturbation analysis (IPA) estimators of derivatives of steady-state means for a broad class of systems. Our results substantially extend previously available results on steady-state derivative estimation via IPA.

In recent years, there has been a surge of research into methods for estimating derivatives of performance measures from sample paths of stochastic systems. In the case of queueing systems, typical performance measures are mean queue lengths, throughputs, etc., and the derivatives estimated are with respect to system parameters, such as parameters of service and interarrival time distributions. Derivative estimates potentially offer a general means of optimizing performance, and are useful in sensitivity analysis.

In many important combinatorial optimization problems, such as bin packing, allocating customer classes to queueing facilities, vehicle routing, multi-item inventory replenishment and combined routing/inventory control, an optimal partition into groups needs to be determined for a finite collection of objects; each is characterized by a single attribute. The cost is often separable in the groups and the group cost often depends on the cardinality and some aggregate measure of the attributes, such as the sum or the maximum element.

We empirically explore the accuracy of an easily computed approximation for long run, average performance measures such as expected delay and probability of delay in multiserver queueing systems with exponential service times and periodic (sinusoidal) Poisson arrival processes. The pointwise stationary approximation is computed by integrating over time (that is taking the expectation of) the formula for the stationary performance measure with the arrival rate that applies at each point in time.

Monetary models based on cash-in-advance constraints make strong predictions about the stochastic properties of endogeneous variables such as the velocity of circulation of money, the rate of inflation, and real and nominal interest rates. We develop numerical methods to understand these predictions because the models cannot be characterized analytically. We calibrate some cash-in-advance models using driving processes estimated from U. S. time-series data to generate model predictions that are compared to sample statistics.

A conceptual model is developed that describes the relationships among consumer values, utility, and ownership of durables. These relationships are tested empirically using data on a variety of discretionary durables collected from a sample of 735 adults. Results support the model structure and suggest that augmenting the List of Values (Kahle 1983) with a measure of materialism improves prediction of value-related consumer behavior.

This paper concerns production allocation in multicell manufacturing systems. The production objective is to track a nonstationary demand as closely as possible when the demand is near or exceeds the capacity of the system. The contribution of this paper is threefold. First, a series of approximations are proposed to obtain a model that is realistic while admitting a tractable solution. Second, we derive a general result on the second-order finite-time (transient) statistics of a continuous-time Markov chain.

This article provides confirmatory evidence of the value-relevance of book values of oil and gas properties. Harris and Ohlson (1987) find that the book values correlate significantly with the inferred market values of oil and gas properties. Reserve recognition accounting requires the simultaneous publication of alternative measures that are often assumed to be more relevant values of the oil and gas properties.

A meta-analysis of results from 320 published studies relates environmental, strategic, and organizational factors to financial performance. The 320 empirical studies that were reviewed were published between 1921 and 1987. Findings from the most frequently studied relationships include: 1. Industry concentration was addressed in almost 100 studies; over 1,100 tests show a clear directional effect. 2. Growth, analyzed in 88 studies, is consistently related to higher financial performance. 3. Market share is positively associated with financial performance. 4.

A number of issues that relate to the desirability and implications of new venture financing are examined within a principal-agent framework that captures the essence of the relationship between entrepreneurs and venture capitalists. The model suggests: (1) As long as the skill levels of entrepreneurs are common knowledge, all will choose to involve venture capital investors, since the risk sharing provided by outside participation dominates the agency relationship that is created.

In estimating functions of continuous-time Markov chains via simulation, one may reduce variance and computation by simulating only the embedded discrete-time chain. To estimate derivatives (with respect to transition probabilities) of functions of discrete-time Markov chains, we propose embedding them in continuous-time processes. To eliminate the additional variance and computation thereby introduced, we convert back to discrete time. For a restricted class of chains, we may embed in a continuous-time Markov chain and apply perturbation analysis estimation.

A new high-performance algorithmic switched-current memory cell with greatly improved charge injection per- formance is described. The new cell uses algorithmic means to achieve an improvement in charge injection of two orders of magnitude and does not rely on matching.

We argue that although decentralization has advantages in finding low-cost solutions, these advantages are accompanied by coordination problems, which lead to delay or duplication of effort or both. Consequently, decentralization is desirable when there is little urgency or a great deal of private information, but it is strictly undesirable in urgent problems when private information is less important. We also examine the effect of large numbers and find that coordination problems disappear in the limit if distributions are common knowledge.

Similarity scaling often requires subjects to produce such a large number of judgments that fatigue may become a problem. Yet it remains unclear just how respondent fatigue affects similarity perceptions and resulting judgments. The present study uses a categorization perspective to examine the effects of fatigue on similarity judgments. The results suggest that subjects rely increasingly on category membership as they progress through a similarity judgment task.

Meta-analysis has become a popular approach for studying systematic variation in parameter estimates across studies. This article discusses the use of meta-analysis results as prior information in a new study. Although hierarchical prior distributions in a traditional Bayesian framework are characterized by complete exchangeability, meta-analysis priors explicitly incorporate heterogeneity in prior vectors.

A shopping mall, new office towers, a convention center, an atrium hotel, a restored historic neighborhood. These are the civic agenda for downtown development in the last third of the twentieth century, a trophy collection that mayors want. Add a domed stadium, aquarium, or cleaned-up waterfront to suit the circumstances, and you have the essential equipment for a first-class American city.

This article presents an exploratory investigation into longitudinal patterns of influence in group decision-making. In particular, we focus on how the outcomes of past decisions affect group members' relative influence in future joint decisions. Results suggest that past outcomes play an important role in the resolution of disagreements when group member preferences are equally intense. Losers in prior decisions are likely to win in the future (and vice versa) due to what appears to be promotion of equity in the group.

In most vehicle routing problems, a given set of customers is to be partitioned into a collection of regions each of which is assigned to a single vehicle starting at a depot and returning there after visiting all of the region's customers exactly once in a route. In this paper we consider problem settings where the cost of a route may depend on its length ϑ as well as m, the number of points on the route, according to some general function f(ϑ,m), assumed to be nondecreasing and concave in ϑ.

A central assumption of meta-analysis is that the sample of studies fairly represents all work done in the field, published and unpublished. However, if studies with "poor" results are less likely to be published, a potential publication bias is present. The authors propose a maximum likelihood approach to estimating publication bias for the situation in which censorship based on effect size may occur. An explicit hypothesis test is provided for testing whether or not censorship is present.

By committing to terminate funding if a firm's performance is poor, investors can mitigate managerial incentive problems. These optimal financial constraints, however, encourage rivals to ensure that a firm's performance is poor; this raises the chance that the financial constraints become binding and induce exit. We analyze the optimal financial contract in light of this predatory threat. The optimal contract balances the benefits of deterring predation by relaxing financial constraints against the cost of exacerbating incentive problems. (JEL 610)

The ultimate success of new product R&D depends as much on customer acceptance as on technological breakthroughs. In this article, Susan Holak and Donald Lehmann focus on customer acceptance by exploring the manner in which the general attributes of Rogers (relative advantage, compatibility, complexity, divisibility and communicability) plus perceived risk combine to form the intention to buy an innovation. Results demonstrate a causal structure among these attributes and lead to various implications for R&D guidelines and product design.

PASTA (Poisson Arrivals See Time Averages) is a term coined by R. Wolff in his well known 1982 paper. In keeping with Wolff's terminology, we use the term anti-PASTA to refer to the following converse of PASTA. Given that arrivals do indeed see time averages, when must the arrival process necessarily be Poisson? We show that anti-PASTA is satisfied in a pure-jump Markov process, provided that the arrival process corresponds to a subset of the Markov process jumps.

Research on object concepts has identified one level of abstraction as "basic" in cognition and communication. We investigated whether concepts for routine social events have a basic level by replicating the converging operations used to investigate object concepts. In Experiment I, subjects were presented with event names from a taxonomy and were asked to list the actions comprising the event.

I construct an intertemporal model in which investors trade shares of a firm. All trading is done through competitive market makers. After the initial period and before the end of the planning horizon, information is asymmetrically distributed among traders, and the prices for investors who buy shares are higher than for those who sell shares. The presence of this deviation from the Walrasian paradigm notwithstanding, dividend policy does not affect the initial period's share price or shareholders' welfare. This result is robust to various extensions of the model.

Federal cutbacks in urban aid in the 1970s forced cities to finance redevelopment projects with their own resources. Freed from federal rules and regulations, cities responded with invention, devising new financial strategies that proved to be powerful alternatives to direct federal aid. The process that fostered the solutions—public-private dealmaking—transformed the nature of city development practice, raising with it troublesome issues of accountability. This article describes these financial strategies and the nature of public subsidies in the deals.

Literature concerning the quality of individual and face-to-face group judgments has generally concluded that both groups and statistically pooled individuals outperform randomly chosen or average individuals. This paper extends previous research by comparing statistically pooled individual judgments of both individuals and face-to-face groups in a stock selection task. In general, decisions that would have resulted from statistically pooled judgments were better (as assessed by future stock value) than those that would have resulted from individual or face-to-face group judgments.