María José Muñoz Torrecillas

Hesitant Fuzzy Worth

Graphical abstractDisplay Omitted HighlightsInnovative methodology for ranking hesitant fuzzy sets based on Social Choice.Novel application 1: real problem of ranking universities via metarankings.Novel application 2: procedure for improving teaching performance assessments.New justification of the theoretical model by hesitant fuzzy sets. We introduce a novel methodology for ranking hesitant fuzzy sets. It builds on a recent, theoretically sound contribution in Social Choice. In order to justify the applicability of such analysis, we develop two real implementations: (i) new metarankings of world academic institutions that build on real data from three reputed agencies, and (ii) a new procedure for improving teaching performance assessments which we illustrate with real data collected by ourselves.

A comparison of three Hurst exponent approaches to predict nascent bubbles in S&P500 stocks

In this paper, three approaches to calculate the self-similarity exponent of a time series are compared in order to determine which one performs best to identify the transition from random efficient market behavior (EM) to herding behavior (HB) and hence, to find out the beginning of a market bubble. In particular, classical Detrended Fluctuation Analysis (DFA), Generalized Hurst Exponent (GHE) and GM2 (one of Geometric Method-based algorithms) were applied for self-similarity exponent calculation purposes. Traditionally, researchers have been focused on identifying the beginning of a crash. Instead of this, we are pretty interested in identifying the beginning of the transition process from EM to a market bubble onset, what we consider could be more interesting. The relevance of self-similarity index in such a context lies on the fact that it becomes a suitable indicator which allows to identify the raising of HB in financial markets. Overall, we could state that the greater the self-similarity exponent in financial series, the more likely the transition process to HB could start. This fact is illustrated through actual S\&P500 stocks.

Measuring Impatience in Intertemporal Choice.

In general terms, decreasing impatience means decreasing discount rates. This property has been usually referred to as hyperbolic discounting, although there are other discount functions which also exhibit decreasing discount rates. This paper focuses on the measurement of the impatience associated with a discount function with the aim of establishing a methodology to compare this characteristic for two different discount functions. In this way, first we define the patience associated with a discount function in an interval as its corresponding discount factor and consequently we deduce that the impatience at a given moment is the corresponding instantaneous discount rate. Second we compare the degree of impatience of discount functions belonging to the same or different families, by considering the cases in which the functions do or do not intersect.

Valuation Fuzzy Soft Sets: A Flexible Fuzzy Soft Set Based Decision Making Procedure for the Valuation of Assets

Zadeh’s fuzzy set theory for imprecise or vague data has been followed by other successful models, inclusive of Molodtsov’s soft set theory and hybrid models like fuzzy soft sets. Their success has been backed up by applications to many branches like engineering, medicine, or finance. In continuation of this effort, the purpose of this paper is to put forward a versatile methodology for the valuation of goods, particularly the assessment of real state properties. In order to reach this target, we develop the concept of (partial) valuation fuzzy soft set and introduce the novel problem of data filling in partial valuation fuzzy soft sets. The use of fuzzy soft sets allows us to quantify the qualitative attributes involved in an assessment context. As a result, we illustrate the effectiveness and validity of our valuation methodology with a real case study that uses data from the Spanish real estate market. The main contribution of this paper is the implementation of a novel methodology, which allows us to assess a large variety of assets where data are heterogeneous. Our technique permits to avoid the appraiser’s subjectivity (exhibited by practitioners in housing valuation) and the well-known disadvantages of some alternative methods (such as linear multiple regression).

Observed and Normative Discount Functions in Addiction and other Diseases

The aim of this paper is to find a suitable discount function able to describe the progression of a certain addiction or disease under treatment as a discounting process. In effect, a certain indicator related to a disease decays over time in a manner which is mathematically similar to the way in which discounting has been modeled. We analyze the discount functions observed in experiments which study addictive and other problematic behaviors as well as some alternative hyperbola-like discount functions in order to fit the patience exhibited by the subject after receiving the treatment. Additionally, it has been experimentally found that people with addiction display high rates of discount (impatience) and preference reversals (dynamic inconsistency). This excessive discounting must be correctly modeled by a suitable discount function, otherwise, it can become a trans-disease process underlying addiction and other disorders. The (generalized) exponentiated hyperbolic discount function is proposed to describe the progression of a disease with respect to the treatment, since it maintains the property of inconsistency by exhibiting a decreasing discount rate after an initial period in which the opposite occurs.

Identifying the Transition from Efficient-Market to Herding Behavior: Using a Method from Econophysics

ABSTRACT We test whether “detrended fluctuation analysis” (DFA)—an econophysics method—identifies the transition from efficient-market trading to herding behavior and the rise of the NASDAQ dot.com stock market bubble. DFA divides a time series into “segments” of varying lengths and then tests whether power-law distributions exist within the segments. A power-law distribution of stock-price changes within a segment indicates herding behavior and the start of the dot.com bubble. The clarity of the transition indication depends on both segment lengths and segment starting dates. Our findings show that DFA can be used to identify the beginning of stock-market bubbles but not the beginning of crashes.

Delay and Interval Effects with Subadditive Discounting Functions

Delay effect appears as an anomaly of the traditional discounted utility model according to which a decrease of the discount rate is performed as waiting time increases. But, in this description, it is not clear if the benchmark (that is to say, the reference instant in the assessment process) or the discounted amount availability is fixed or variable. In this way, other authors use the term common difference effect (and immediacy effect, when the first outcome is available immediately) and this expression at least does implies a variable discounted amount availability. Read introduces another different effect, the interval effect: longer intervals lead to smaller values of the discount rate r. Taking into account the parameter δ (geometric mean of the discount factor), the interval effect implies larger values of δ. In this paper we try to clarify the concepts of delay and interval effect and we deduce some relationships between these concepts and certain subadditive discounting functions.

Impatience and Inconsistency in Intertemporal Choice: An Experimental Analysis

ABSTRACT In this article the experiment carried out by Takahashi et al. [2009] is replicated to analyze the influence of culture, gender, origin (urban or rural), and socioeconomic level on the impulsivity and consistency of decision-making processes concerning monetary gains and losses. The results indicate that Spanish students show inconsistency, and more impulsivity over gains (i.e., more impatience, as they discount delayed outcomes more rapidly) than do Japanese and American students. Additionally, participants from urban areas show more impatience over gains than do participants from rural ones, women are more impatient than men are over losses, and participants of different socioeconomic levels show differences in their impulsivity parameters.

Self-Control in Intertemporal Choice and Mediterranean Dietary Pattern

Background: The Mediterranean Diet (hereinafter MD) is considered a healthy dietary pattern. Adherence to this pattern can be assessed by means of the KIDMED test by which individuals are assigned an index and classified into three groups of adherence to MD: high, medium, and low. In addition, impulsivity or impatience in intertemporal choice has been defined as a strong preference for small immediate rewards over large delayed ones. Objective: This study examines the relationship between dietary habits, specifically Mediterranean dietary pattern, measured by the KIDMED index, and the exhibited impatience in intertemporal choices, by means of the parameter k (discount rate of the hyperbolic discount function). Methods: A sample of 207 university students answered a questionnaire based on two tests: the KIDMED test, to assess the degree of adherence to MD, and an intertemporal choice questionnaire, to assess impatience or impulsivity. Individuals were grouped depending on their KIDMED score and then the discount rate or impulsivity parameter was calculated for each group. Results: Discount rates were inversely related to the degree of adherence to MD. The values of overall k were 1.53, 1.91, and 3.71% for the groups exhibiting high, medium and low adherence to MD, respectively. We also found higher k-values for larger rewards (magnitude effect) in the three groups. Conclusion: High adherence to MD is related to less steep time discounting, which implies less impulsivity (more self-control) or lower discount rates. Conversely, low adherence to MD is related to steeper time discounting, which implies impulsivity or higher discount rates. These findings could be used to identify the target population where policy interventions are needed in order to promote healthier diet habits.

A multifactor approach to the social discount rate: An application to the Spanish forest system

ABSTRACT This paper focuses on the calculation of the social discount rate to be used in the valuation of long-term investment projects and, more specifically, in the appraisal of public and environmental projects. The key idea is that the instantaneous discount rate of the discount function used for valuation must be equal to the hazard rate of the public good or the mortality rate of the population affected by the project. Previously, this approach has been applied by the authors to a system in which failure depends on a single component, but in this paper, we are going to consider the failure of several independent components which, in combination, give rise to a multivariate hazard rate. In our empirical application, the entire forested area of Spain will be the system, and the forests of the seventeen autonomous communities will be considered the components of the system; the forest fire will be the failure, measured by the number of hectares devastated by fire in each region. Finally, once the failure corresponding to all regions has been aggregated in a multivariate hazard rate, it will be implemented as a part of the social discount rate.This paper focuses on the calculation of the social discount rate to be used in the valuation of long-term investment projects and, more specifically, in the appraisal of public and environmental p...