Detecting gradual changes in locally stationary processes

In a wide range of applications, the stochastic properties of the observed time series change over time. The changes often occur gradually rather than abruptly: the properties are (approximately) constant for some time and then slowly start to change. In many cases, it is of interest to locate the time point where the properties start to vary. In contrast to the analysis of abrupt changes, methods for detecting smooth or gradual change points are less developed and often require strong parametric assumptions. In this paper, we develop a fully nonparametric method to estimate a smooth change point in a locally stationary framework. We set up a general procedure which allows us to deal with a wide variety of stochastic properties including the mean, (auto)covariances and higher moments. The theoretical part of the paper establishes the convergence rate of the new estimator. In addition, we examine its finite sample performance by means of a simulation study and illustrate the methodology by two applications to financial return data.Comment: Published at http://dx.doi.org/10.1214/14-AOS1297 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Derivation of forest inventory parameters from high-resolution satellite imagery for the Thunkel area, Northern Mongolia. A comparative study on various satellite sensors and data analysis techniques.

With the demise of the Soviet Union and the transition to a market economy starting in the 1990s, Mongolia has been experiencing dramatic changes resulting in social and economic disparities and an increasing strain on its natural resources. The situation is exacerbated by a changing climate, the erosion of forestry related administrative structures, and a lack of law enforcement activities. Mongolia’s forests have been afflicted with a dramatic increase in degradation due to human and natural impacts such as overexploitation and wildfire occurrences. In addition, forest management practices are far from being sustainable. In order to provide useful information on how to viably and effectively utilise the forest resources in the future, the gathering and analysis of forest related data is pivotal. Although a National Forest Inventory was conducted in 2016, very little reliable and scientifically substantiated information exists related to a regional or even local level. This lack of detailed information warranted a study performed in the Thunkel taiga area in 2017 in cooperation with the GIZ. In this context, we hypothesise that (i) tree species and composition can be identified utilising the aerial imagery, (ii) tree height can be extracted from the resulting canopy height model with accuracies commensurate with field survey measurements, and (iii) high-resolution satellite imagery is suitable for the extraction of tree species, the number of trees, and the upscaling of timber volume and basal area based on the spectral properties. The outcomes of this study illustrate quite clearly the potential of employing UAV imagery for tree height extraction (R2 of 0.9) as well as for species and crown diameter determination. However, in a few instances, the visual interpretation of the aerial photographs were determined to be superior to the computer-aided automatic extraction of forest attributes. In addition, imagery from various satellite sensors (e.g. Sentinel-2, RapidEye, WorldView-2) proved to be excellently suited for the delineation of burned areas and the assessment of tree vigour. Furthermore, recently developed sophisticated classifying approaches such as Support Vector Machines and Random Forest appear to be tailored for tree species discrimination (Overall Accuracy of 89%). Object-based classification approaches convey the impression to be highly suitable for very high-resolution imagery, however, at medium scale, pixel-based classifiers outperformed the former. It is also suggested that high radiometric resolution bears the potential to easily compensate for the lack of spatial detectability in the imagery. Quite surprising was the occurrence of dark taiga species in the riparian areas being beyond their natural habitat range. The presented results matrix and the interpretation key have been devised as a decision tool and/or a vademecum for practitioners. In consideration of future projects and to facilitate the improvement of the forest inventory database, the establishment of permanent sampling plots in the Mongolian taigas is strongly advised.2021-06-0

How Product Assortments Affect Buyer Preferences: Empirical Analysis of the Robustness of the Compromise Effect

Behavioral research revealed that product assortments can influence buyer preferences and affect purchase decisions between options of a product line. In this article, the compromise effect is investigated according to which the share of a product is expected to increase when it is in an intermediate position in an assortment subset. Since most of the previous studies on the compromise effect used artificial designs that lack realism, a limited external validity of experimental findings is to be supposed. This is a drawback, especially when decisions about compositions of real product lines should be supported. Therefore, an enhanced experimental design is presented with subjects making unforced and binding choices between real brands, which is similar to regular purchase decisions. Although results of our studies prove robustness, the magnitude of the compromise effect is significantly reduced in such real marketplace scenarios hence notably influencing predictions of sales and profitability of product lines.Consumer Behavior; Compromise Effect; Consumer Preferences; Assortment Planning; Experimental Design; Choice in Context

When Judgments and Preferences Fail to Conform: Research on Preference Reversals for Product Purchases

In this paper, the preference reversal phenomenon known from risk research is investigated according to which subjects prefer gamble A over B in competitive decisions although they reveal higher valuations in terms of a cash equivalent (CE) or a willingness to pay (WTP) for the latter when gambles are assessed separately in monadic judgments. In contrast to the experimental settings of research on risky choices, our studies observed unforced and binding purchase decisions of experienced consumers between real products in natural shopping environments. Results confirm robustness of preference reversals in risk-free purchase decisions indicating that orderings of product preferences reverse significantly between evaluations in monadic and competitive designs. While recent pricing research has been largely focused on monadic designs and suggested BDM mechanisms or second-price auctions for elicitations of consumers’ true willingness to pay, results of our studies indicate a substantial discrepancy between preference orders based on monadic judgments and preferences that consumers reveal in competitive purchase decisions.Preference Reversals, Willingness to Pay, Monadic Designs, Competitive Designs, Pricing Research, Procedure Invariance

Experimental evidence of context-dependent preferences in risk-free settings

This study investigates context effects in general and the compromise effect in particular. It is argued that earlier research in this area lacks realism, a shortcoming that is a major drawback to research conclusions and stated management implications. The importance of this issue is stressed by previous research showing that behavioral anomalies found in hypothetical experimental settings tend to be significantly reduced when real payoff mechanisms are introduced. Therefore, to validate the compromise effect, an enhanced design is presented with participants making binding purchase decisions in the laboratory. We find that the compromise effect holds for real purchase decisions, and therefore is validated, and is not an artificial effect in surveys on hypothetical buying decisions. While conclusions and implications for marketing managers, derived in previous work assume that context effects hold for real market decisions, the results created by this enhanced design close this gap in the literature. --decision-making,anomalies,irrelevant alternatives,context effects

When Judgments and Preferences Fail to Conform: Research on Preference Reversals for Product Purchases

In this paper, the preference reversal phenomenon known from risk research is investigated according to which subjects prefer gamble A over B in competitive decisions although they reveal higher valuations in terms of a cash equivalent (CE) or a willingness to pay (WTP) for the latter when gambles are assessed separately in monadic judgments. In contrast to the experimental settings of research on risky choices, our studies observed unforced and binding purchase decisions of experienced consumers between real products in natural shopping environments. Results confirm robustness of preference reversals in risk-free purchase decisions indicating that orderings of product preferences reverse significantly between evaluations in monadic and competitive designs. While recent pricing research has been largely focused on monadic designs and suggested BDM mechanisms or second-price auctions for elicitations of consumers\u27 true willingness to pay, results of our studies indicate a substantial discrepancy between preference orders based on monadic judgments and preferences that consumers reveal in competitive purchase decisions

How Product Assortments Affect Buyer Preferences: Empirical Analysis of the Robustness of the Compromise Effect

Behavioral research revealed that product assortments can influence buyer preferences and affect purchase decisions between options of a product line. In this article, the compromise effect is investigated according to which the share of a product is expected to increase when it is in an intermediate position in an assortment subset. Since most of the previous studies on the compromise effect used artificial designs that lack realism, a limited external validity of experimental findings is to be supposed. This is a drawback, especially when decisions about compositions of real product lines should be supported. Therefore, an enhanced experimental design is presented with subjects making unforced and binding choices between real brands, which is similar to regular purchase decisions. Although results of our studies prove robustness, the magnitude of the compromise effect is significantly reduced in such real marketplace scenarios hence notably influencing predictions of sales and profitability of product lines

Fact or Artifact: Does the compromise effect occur when subjects face real consequences of their choices?

This study investigates context effects in general and the compromise effect in particular. It is argued that earlier research in this area lacks realism which is a major drawback to research conclusions and stated management implications. The importance of this issue is stressed by previous research showing that behavioral anomalies found in hypothetical experimental settings tend to be significantly reduced when real payoff mechanisms are introduced. Therefore, to validate the compromise effect, an enhanced experimental design is presented with participants making choices in the laboratory that are binding. We find that the compromise effect holds for real purchase decisions, and therefore is validated and not an artificial effect in surveys on hypothetical buying decisions. While conclusions and implications for marketing managers derived in previous work assume that context effects hold for real market decisions, the results created by this enhanced design close this gap in marketing literature