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Now showing 1 - 10 of 297
  • Publication
    Forest Management under Uncertainty
    (2011-10-01) Alonso-Ayuso, Antonio; Escudero, Laureano F; Guignard, Monique; Quinteros, Martín; Weintraub, Andres
    The forest harvest and road construction planning problem consists fundamentally of managing land designated for timber production and divided into harvest cells. For each time period the planner must decide which cells to cut and what access roads to build in order to maximize expected net profit. We have previously developed deterministic mixed integer linear programming models for this problem. The main contribution of the present work is the introduction of a multistage Stochastic Integer Programming model. This enables the planner to make more robust decisions based on a range of timber price scenarios over time, maximizing the expected value instead of merely analyzing a single average scenario. We use a specialization of the Branch-and-Fix Coordination algorithmic approach. Different price and associated probability scenarios are considered, allowing us to compare expected profits when uncertainties are taken into account and when only average prices are used. The stochastic approach as formulated in this work generates solutions that were always feasible and better than the average solution, while the latter in many scenarios proved to be infeasible.
  • Publication
    P-curve: A Key to The File Drawer
    (2014-01-01) Simonsohn, Uri; Nelson, Leif. D; Simmons, Joseph. P
    Because scientists tend to report only studies (publication bias) or analyses (p-hacking) that “work,” readers must ask, “Are these effects true, or do they merely reflect selective reporting?” We introduce p-curve as a way to answer this question. P-curve is the distribution of statistically significant p values for a set of studies (ps .05). Because only true effects are expected to generate right-skewed p-curves— containing more low (.01s) than high (.04s) significant p values— only right-skewed p-curves are diagnostic of evidential value. By telling us whether we can rule out selective reporting as the sole explanation for a set of findings, p-curve offers a solution to the age-old inferential problems caused by file-drawers of failed studies and analyses.
  • Publication
    Political Affiliation Affects Adaptation to Climate Risks: Evidence from New York City
    (2016-09-01) Wouter Botzen, W. J; Michel-Kerjan, Erwann; Kunreuther, Howard; de Moel, Hans; Aerts, Jeroen C.J.H
    Research reveals that liberals and conservatives in the United States diverge about their beliefs regarding climate change. We show empirically that political affiliation also matters with respect to climate related risks such as flooding from hurricanes. Our study is based on a survey conducted 6 months after Superstorm Sandy in 2012 of over 1,000 residents in flood-prone areas in New York City. Democrats’ perception of their probability of suffering flood damage is significantly higher than Republicans’ and they are also more likely to invest in individual flood protection measures. However, 50% more Democrats than Republicans in our sample expect to receive federal disaster relief after a major flood. These results highlight the importance of taking into account value-based considerations in designing disaster risk management policies.
  • Publication
    Managing Demand and Sales Dynamics in New Product Diffusion Under Supply Constraint
    (2002-02-01) Ho, Teck Hua; Savin, Sergei; Terwiesch, Christian
    The Bass diffusion model is a well-known parametric approach to estimating new product demand trajectory over time. This paper generalizes the Bass model by allowing for a supply constraint. In the presence of a supply constraint, potential customers who are not able to obtain the new product join the waiting queue, generating backorders and potentially reversing their adoption decision, resulting in lost sales. Consequently, they do not generate the positive “word-of-mouth” that is typically assumed in the Bass model, leading to significant changes in the new product diffusion dynamics. We study how a firm should manage its supply processes in a new product diffusion environment with backorders and lost sales. We consider a make-to-stock production environment and use optimal control theory to establish that it is never optimal to delay demand fulfillment. This result is interesting because immediate fulfillment may accelerate the diffusion process and thereby result in a greater loss of customers in the future. Using this result, we derive closed-form expressions for the resulting demand and sales dynamics over the product life cycle. We then use these expressions to investigate how the firm should determine the size of its capacity and the time to market its new product. We show that delaying a product launch to build up an initial inventory may be optimal and can be used as a substitute for capacity. Also, the optimal time to market and capacity increase with the coefficients of innovation and imitation in the adoption population. We compare our optimal capacity and time to market policies with those resulting from exogeneous demand forecasts in order to quantify the value of endogenizing demand.
  • Publication
    Using Implementation Intentions Prompts to Enhance Influenza Vaccination Rates
    (2011-06-01) Milkman, Katherine L; Beshears, John; Choi, James J; Laibson, David; Madrian, Brigitte C
    We evaluate the results of a field experiment designed to measure the effect of prompts to form implementation intentions on realized behavioral outcomes. The outcome of interest is influenza vaccination receipt at free on-site clinics offered by a large firm to its employees. All employees eligible for study participation received reminder mailings that listed the times and locations of the relevant vaccination clinics. Mailings to employees randomly assigned to the treatment conditions additionally included a prompt to write down either (i) the date the employee planned to be vaccinated or (ii) the date and time the employee planned to be vaccinated. Vaccination rates increased when these implementation intentions prompts were included in the mailing. The vaccination rate among control condition employees was 33.1%. Employees who received the prompt to write down just a date had a vaccination rate 1.5 percentage points higher than the control group, a difference that is not statistically significant. Employees who received the more specific prompt to write down both a date and a time had a 4.2 percentage point higher vaccination rate, a difference that is both statistically significant and of meaningful magnitude.
  • Publication
    Achieving Breakthrough Service Delivery Through Dynamic Asset Deployment Strategies
    (2006-06-01) Cohen, Morris. A; Agrawal, Narendra; Agrawal, Vipul
    Many firms have shifted their focus from their products to their customers and the value derived from owning and using the products. They see after-sales service as an important source of revenue and profit, customer acquisition and retention, and competitive differentiation. However, they also find it challenging to manage their service-supply chain. Service organizations must position and manage service-supply-chain resources optimally to support the delivery of after-sales service. They must also develop capabilities to respond rapidly to the demand for service in a cost-effective manner. To succeed in implementing a service-centric strategy, firms must determine what items in their products’ service bill-of-material hierarchy should be deployed throughout their geographical hierarchy of service support locations. They must make these complex and interrelated decisions in anticipation of service demand, which is uncertain. Firms must also be flexible and should understand the mechanisms in a service-supply chain needed to fulfill customers’ demands for service and the resulting demands for support assets and capacities. Dynamic asset deployment (DAD), a collection of management policies that promote this flexibility, can be used to develop the capabilities needed to effectively and profitably deliver services. These policies require a real-options-based optimization approach to decision making.
  • Publication
    Communication and Uncertainty in Concurrent Engineering
    (1998-08-01) Loch, Christoph. H; Terwiesch, Christian
    We present an analytical model of concurrent engineering, where an upstream and a down-stream task are overlapped to minimize time-to-market. The gain from overlapping activities must be weighed against the delay from rework that results from proceeding in parallel based on preliminary information. Communication reduces the negative effect of rework at the expense of communication time. We derive the optimal levels of concurrency combined with communication, and we analyze how these two decisions interact in the presence of uncertainty and dependence. Uncertainty is modeled via the average rate of engineering changes, and its reduction via the change of the modification rate over time. In addition, we model dependence by the impact the modifications impose on the downstream task. The model yields three main results. First, we present a dynamic decision rule for determining the optimal meeting schedule. The optimal meeting frequency follows the frequency of engineering changes over time, and it increases with the levels of uncertainty and dependence. Second, we derive the optimal concurrency between activities when communication follows the optimal pattern described by our decision rule. Uncertainty and dependence make concurrency less attractive, reducing the optimal overlap. However, the speed of uncertainty reduction may increase or decrease optimal overlap. Third, choosing communication and concurrency separately prevents achieving the optimal time-to-market, resulting in a need for coordination.
  • Publication
    Research Note—User Design of Customized Products
    (2007-03-01) Randall, Taylor; Terwiesch, Christian; Ulrich, Karl
    User design offers tantalizing potential benefits to manufacturers and consumers, including a closer match of products to user preferences, which should result in a higher willingness to pay for goods and services. There are two fundamental approaches that can be taken to user design: parameter-based systems and needs-based systems. With parameter-based systems, users directly specify the values of design parameters of the product. With needs-based systems, users specify the relative importance of their needs, and an optimization algorithm recommends the combination of design parameters that is likely to maximize user utility. Through an experiment in the domain of consumer laptop computers, we show that for parameter-based systems, outcomes, including measures for comfort and fit, increase with the expertise of the user. We also show that for novices, the needs-based interface results in better outcomes than the parameter-based interface.
  • Publication
    Optimal Credit Swap Portfolios
    (2014-09-01) Giesecke, Kay; Kim, Baeho; Kim, Jack; Tsoukalas, Gerry
    This paper formulates and solves the selection problem for a portfolio of credit swaps. The problem is cast as a goal program that entails a constrained optimization of preference-weighted moments of the portfolio value at the investment horizon. The portfolio value takes account of the exact timing of protection premium and default loss payments, as well as any mark-to-market profits and losses realized at the horizon. The constraints address collateral and solvency requirements, initial capital, position limits, and other trading constraints that credit swap investors often face in practice. The multimoment formulation accommodates the complex distribution of the portfolio value, which is a nested expectation under risk-neutral and actual probabilities. It also generates computational tractability. Numerical results illustrate the features of optimal portfolios. In particular, we find that credit swap investment constraints can have a significant impact on optimal portfolios, even for simple investment objectives. Our problem formulation and solution approach extend to corporate bond portfolios and mixed portfolios of corporate bonds and credit derivatives.
  • Publication
    Deriving the Pricing Power of Product Features by Mining Consumer Reviews
    (2011-08-01) Archak, Nikolay; Ghose, Anindya; Ipeirotis, Panagiotis G
    Increasingly, user-generated product reviews serve as a valuable source of information for customers making product choices online. The existing literature typically incorporates the impact of product reviews on sales based on numeric variables representing the valence and volume of reviews. In this paper, we posit that the information embedded in product reviews cannot be captured by a single scalar value. Rather, we argue that product reviews are multifaceted, and hence the textual content of product reviews is an important determinant of consumers' choices, over and above the valence and volume of reviews. To demonstrate this, we use text mining to incorporate review text in a consumer choice model by decomposing textual reviews into segments describing different product features. We estimate our model based on a unique data set from Amazon containing sales data and consumer review data for two different groups of products (digital cameras and camcorders) over a 15-month period. We alleviate the problems of data sparsity and of omitted variables by providing two experimental techniques: clustering rare textual opinions based on pointwise mutual information and using externally imposed review semantics. This paper demonstrates how textual data can be used to learn consumers' relative preferences for different product features and also how text can be used for predictive modeling of future changes in sales.