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AbstractSince 2000, after the Water Framework Directive came into force, aquatic ecosystems' bioassessment has acquired immense practical importance for water management. Currently, due to extensive scientific research and monitoring, we have gathered comprehensive hydrobiological databases. The amount of available data increases with each subsequent year of monitoring, and the efficient analysis of these data requires the use of proper mathematical tools. Our study challenges the comparison of the modelling potential between four indices for the ecological status assessment of lakes based on three groups of aquatic organisms, i.e. phytoplankton, phytobenthos and macrophytes. One of the deep learning techniques, artificial neural networks, has been used to predict values of four biological indices based on the limited set of the physicochemical parameters of water. All analyses were conducted separately for lakes with various stratification regimes as they function differently. The best modelling quality in terms of high values of coefficients of determination and low values of the normalised root mean square error was obtained for chlorophyll a followed by phytoplankton multimetric. A lower degree of fit was obtained in the networks for macrophyte index, and the poorest model quality was obtained for phytobenthos index. For all indices, modelling quality for non-stratified lakes was higher than this for stratified lakes, giving a higher percentage of variance explained by the networks and lower values of errors. Sensitivity analysis showed that among physicochemical parameters, water transparency (Secchi disk reading) exhibits the strongest relationship with the ecological status of lakes derived by phytoplankton and macrophytes. At the same time, all input variables indicated a negligible impact on phytobenthos index. In this way, different explanations of the relationship between biological and trophic variables were revealed.

Abstract. Assessing the risk of complex systems to natural hazards is an important but challenging problem. In today's intricate socio-technological world,
characterized by strong urbanization and technological trends, the connections and interdependencies between exposed elements are crucial. These
complex relationships call for a paradigm shift in collective risk assessments, from a reductionist approach to a holistic one. Most commonly, the
risk of a system is estimated through a reductionist approach, based on the sum of the risk evaluated individually at each of its elements. In
contrast, a holistic approach considers the whole system to be a unique entity of interconnected elements, where those connections are taken into
account in order to assess risk more thoroughly. To support this paradigm shift, this paper proposes a holistic approach to analyse risk in complex
systems based on the construction and study of a graph, the mathematical structure to model connections between elements. We demonstrate that
representing a complex system such as an urban settlement by means of a graph, and using the techniques made available by the branch of mathematics
called graph theory, will have at least two advantages. First, it is possible to establish analogies between certain graph metrics (e.g. authority,
degree and hub values) and the risk variables (exposure, vulnerability and resilience) and leverage these analogies to obtain a deeper knowledge of
the exposed system to a hazard (structure, weaknesses, etc.). Second, it is possible to use the graph as a tool to propagate the damage into the
system, for not only direct but also indirect and cascading effects, and, ultimately, to better understand the risk mechanisms of natural hazards in
complex systems. The feasibility of the proposed approach is illustrated by an application to a pilot study in Mexico City.

PurposeThe "Internet of Things (IoT)" is a platform for involving smart devices via the Internet at a worldwide scale. It supports the "supply chain (SC)" and "information and communication technology (ICT)" infrastructure to be well integrated into an organization and externally with customers and suppliers. The "sustainable supply chain (SSC)" is currently unavoidable if a company seeks to satisfy the aggressive change in its customers' requirements. Numerous studies have confirmed that manufacturing firms have to accelerate the shift of their focus toward sustainability and the implementation of novel technologies, such as IoT, to accomplish their organizational goals most effectively. Although the literature consists of many theoretical approaches to IoT and numerous studies that have extremely concentrated upon the IoT technology and its potential applications, it lacks research with a focus on the challenges that arise when applying IoT to the "sustainable supply chain management (SSCM)".Design/methodology/approachThe present study proposes an integrated framework using the "Criteria Importance Through Intercriteria Correlation (CRITIC)" and "VlseKriterijumska optimizcija I kaompromisno resenje in Serbian (VIKOR)" models and employs to evaluate the IoT challenges to implement the SSCM. For estimating the criteria weights, the CRITIC tool is utilized. The organization's prioritization is obtained by the VIKOR procedure, which delivers simple mathematical procedures with precise and consistent outcomes.FindingsTo exhibit the practicality of the introduced model, a case study is taken to evaluate the IoT challenges to implement the SSCM within the "q-Rung Orthopair Fuzzy Sets (q-ROFSs)" environment. Moreover, the authors exhibit a sensitivity investigation over given parameter values, examining the stability of developed approach. Finally, the authors draw attention to a comparison between developed q-ROF-CRITIC-VIKOR decision-making approach with an existing q-ROF-TOPSIS method to show its superiority and potency.Originality/valueThe outcome of the study lies in observing the top benefits of individual businesses, and their entire SSCs can be found by implementing IoT. This paper investigates the most important challenges that individual firms and entire SSCs might while applying IoT. It provides a deep insight regarding the effects of IoT upon SSCM and the issues every firm need to contemplate when it is to apply IoT solutions.

The rapid decline in mortality after the end of World War II, in combination with a much slower downward adjustment of fertility, resulted in an extraordinary acceleration of world population growth. In a contribution prepared for the 1959 Vienna conference of the International Union for the Scientific Study of Population, Ansley J. Coale présented a concise and spirited exploration of the influence of mortality and fertility on the levels and patterns of growth and on the distribution of the population by age. Using the stable population model as his tool of exploration, Coale présents a comparative analysis of the implications of movements between stable states, making imaginative illustrative assumptions on changes over time and highlighting the often surprising and counterintuitive results of such calculations. The full text of this article, omitting summaries in English and French, is reproduced below from pp. 36–41 in Union Internationale pour I?étude scientifique de la population, Internationaler Bevölkerungskongress, Wien:Im Selbstverlag, 1959.Ansley Coale was one of the most prominent figures in demography in the second half of the twentieth century. He was born in 1917 and was educated at Princeton University. He spent his entire professional career at Princeton, as a member of the economics faculty and in association with the Office of Population Research, of which he was director from 1959 to 1975. In 1967/68 he was president of the Population Association of America, and from 1977 to 1981 he was president of IUSSP. His many scientific works include Population Growth and Economic Development in Low‐Income Countries (1958), coauthored with Edgar M. Hoover, a book that was highly influential in shaping the international population policy agenda from the 1960s on—lately receiving renewed attention as a predictor of the "demographic dividend" benefiting economies as a result of the transition to low fertility. He was initiator and leader of the Princeton project exploring the causes of the decline in marital fertility in Europe, culminating in the 1986 book, coedited with Susan C. Watkins, The Decline of Fertility in Europe. His most lasting contribution to population studies, however, was in the field of formal demography, as both teacher and scholar. His research in this area is exemplified by the 1972 book The Growth and Structure of Human Populations: A Mathematical Investigation, and in the application of demographic models to the estimation and analysis of population data. Ansley Coale died on 5 November 2002, at the age of 84.

BAUMOL, HILDA and BAUMOL, WILLIAM J. Inflation and the Performing Arts New York/London: New York University Press 1984.CASSON, MARK Economics of Unemployment. An Historical Perspective, Oxford: Martin Robertson 1983FISHER, FRANKLIN M. Disequilibrium Foundations of Equilibrium Economics (Econometric Society Publication, No. 6.), Cambridge/London/ New York: Cambridge University Press 1983FOLKERTS‐LANDAU, D.F.I. Intertemporal Planning, Exchange, and Macroeconomics Cambridge/London/New York: Cambridge University Press 1982JACK E. ADAMS Little Rock FREY, BRUNO S.: International Political Economics, Oxford: Basil Black‐well 1984CHARLES P. KINDLEBERGERLincoln Center, Massachusetts GEORGE, REV. DR. P. P.: Economics of Higher Education in Tamil Nadu, Madras: Centre for Research on New International Economic Order 1984J ANDHYALA B. G. TILAK New Delhi, India DE GIJSEL, PETER et al. (Hrsg.): Ökonomie und Gesellschaft. Jahrbuch 2: Wohlfahrt und Gerechtigkeit, Frankfurt M./New York: Campus 1984WOLFGANG BRANDES/MANFRED KRAFT Paderborn GÖBEL, DIETER: Lebenseinkommen und Erwerbsbiographie. Eine Längs‐schnittuntersuchung mit Daten der gesetzlichen Rentenversicherung (Sonderforschungsbereich 3 der Universitäten Frankfurt und Mannheim), Frankfurt M./New York: Campus 1983SIEGFRIED F. FRANKEFachhochschule für Öffentliche Verwaltung Hamburg GOODWIN, R. M.; KRÜGER, M. and VERCELLI, A. (eds.): Nonlinear Models of Fluctuating Growth. An International Symposium, Siena, Italy 1983 (Lecture Notes in Economics and Mathematical Systems, Vol.228), Berlin/Heidelberg/New York: Springer 1984JOHN T. HARTMANIndiana University GORRES, PETER ANSELM: Die Umverteilung der Arbeit, Beschäftigungs‐, Wachstums‐ und Wohlfahrtseffekte einer Arbeitszeitverkürzung (Reihe Sozialwissenschaftliche Arbeitsmarktforschung, Band 6), Frankfurt/New York: Campus 1984HEINOVMEYER Frankfurt M. HAGEN, OLE and WENSTØP, FRED (eds.): Progress in Utility and Risk Theory (Theory and Decision Library, Vol. 42), Dordrecht/Boston/Lancaster: D. Reidel 1984GEORGES BERNARD CNRS, Paris HOLMLUND, BERTIL: Labor Mobility. Studies of Labor Turnover and Migration in the Swedish Labor Market (The Industrial Institute for Economic and Social Research), Stockholm: Almqvist & Wiksell 1984OLAF HOBLER Hannover KLAMER, ARJO: The New Classical Macroeconomics. Conversations with the New Classical Economists and their Opponents, Brighton: Wheat‐sheaf Books/Harvester Press 1984ALFRED H. BORNEMANNEnglewood LACHMANN, WERNER: Wirtschaftspolitik im Ungleichgewicht (Europai‐sche Hochschulschriften, Reihe V, Band 422), Frankfurt M./Bern/ New York: Peter Lang 1983MCKENZIE, RICHARD B.and TULLOCK, GORDON: Homo oeconomicus. Ökonomische Dimensionen des Alltags, Frankfurt M./New York: Campus 1984MANFRED GÄRTNERBasel MOSLEY, PAUL: The Making of Economic Policy. Theory and Evidence from Britain and the US since 1945, Brighton: Wheatsheaf Books 1984ROMASCO, ALBERT U.The Politics of Recovery: Roosevelt's New Deal, New York: Oxford University Press 1983ROSENSTOCK, ADOLF H.Stabilizing Real Exchange Rates and Rational Expectations (Europäische Hochschulschriften, Reihe V, Band 532), Frankfurt M./Bern/New York: Peter Lang 1984SCHMID, ULRICHWahlkampffinanzierung in den USA und in der Schweiz (Zürcher Beiträge zur Politischen Wissenschaft, Band 8), Diessenhofen: Verlag Rüegger 1985SCHNEIDER, G. and SPRENGER, R.U. (Hrsg.): Mehr Umweltschutz für weniger Geld. Einsatzmöglichkeiten und Erfolgschancen ökonomischer Anreizinstrumente in der Umweltpolitik (ifo‐Studien zur Umweltoko‐nomie, Bd.4), München: ifo‐Institut für Wirtschaftsforschung 1984SIEBERT, HORST (ed.): The Resource Sector in an Open Economy (Lecture Notes in Economics and Mathematical Systems, Vol. 200), Berlin/Heidelberg/New York: Springer 1984.VICARELLI, FAUSTO: Keynes: The Instability of Capitalism, Philadelphia: University of Pennsylvania Press 1984WAGNER, GERT: Umverteilung in der gesetzlichen Rentenversicherung. Eine theoretische und empirische Analyse zum Versicherungsprinzip in der gesetzlichen Rentenversicherung (Sonderforschungsbereich 3 der Universitäten Frankfurt und Mannheim), Frankfurt M./New York: Campus 1984WENZEL, HEINZ‐DIETER: Defizitfinanzierung ah Instrument einer ziel‐orientierten Finanzpolitik. Eine dynamische Analyse (Schriften zur öffentlichen Verwaltung und öffentlichen Wirtschaft, Band 61), Baden‐Baden: Nomos 1983

Introduction. The article continues a series of publications on R-linguistics and is dedicated to the ternary hypothesis and the problem of modeling the world associated with it. The essence of the ternary hypothesis is based on the assumption that any natural language does not use verbs with arity (valency) above three. This hypothesis creates an epistemological problem, the essence of which lies in the mismatch between the constraints of the dimensionality of thinking and the dimensionality of some phenomena and processes of the surrounding world. The indicated problem is directly related to language, since language reflects human thinking and the structure of the world model.Methodology and sources. The results obtained in the previous parts of the series are used as research tools. To develop the necessary mathematical representations for verbs with high valence, the categorization axioms formulated earlier in the series are used.Results and discussion. It has been shown that cases of multiple indirect objects are related to data dependencies in the sentence. Methods of categorization have been developed for ternary relations and relations with higher arity. It has been demonstrated that even in this case, all conditional categorizations and conditional verbs can be reduced to a single categorization.Conclusion. The ternary hypothesis and the ternary problem are formulated. Based on the study of data dependencies, it is shown that the ternary hypothesis is most likely true for all natural languages. Based on the study of methods of categorizing relations with arity higher than three, it is demonstrated that in this case linguistic spaces show stability regardless of the location of categories in the sentence, which makes it possible to describe highdimensional interactions using subordinate clauses. Thus, the appearance of subordinate clauses in all languages of the world is associated with the need to describe highdimensional interactions in the world model human.

The high differentiation of living standards within the boundaries of a complex subject of the Russian Federation actualizes the problems of studying the determinants of financial well-being of the population. The article analyzes four groups of data for Tyumen oblast with autonomous districts that are part of it for the period of 2013–2021, including: average per capita cash income of the population; structural indicators of the balance of monetary income and expenses of the population; volume of deposits and other funds of individuals (excluding escrow accounts); amount of debt on loans provided to resident individuals. We used methods of matching, plotting scattering diagrams, identifying trends. As a result, a number of the following determinants of financial well-being were identified. Among the population of autonomous districts prevails the desire to accumulate savings in the form of cash (by 2021 the amount reached 393 billion rubles). Persistent shortage of cash savings in the South of Tyumen oblast (– 164 billion rubles) is covered by a surplus formed in the districts. In all three RF subjects there is a significant decrease in the ratio of the volume of deposits of the population and the volume of debt on loans, which corresponds to the all-Russian trend. The well-being of the population of the South Tyumen oblast should be considered with the account of the effect of indicative consumption due to the inevitable differentiation in the income of visitors and local population, as well as differences in behavioral models, which consist in a higher degree of wastefulness among visitors. Additionally, the possibility of using the obtained results in the framework of mathematical and neural network modeling of the process of dynamics in the well-being of the Tyumen blast population is considered.

Introduction. R-linguistics uses the axiomatic method in its approach to modeling the world and language [1]. Axioms define the categories of language, their properties and ways of formation. On this basis, when processing the accumulated data in the form of relations, it is possible to form systems of categories and determine the verbs connecting these categories. A reasonable question arises: if categories (to be such) must satisfy certain axioms, does this requirement apply to verbs as well? The purpose of this article is to deal with this issue.Methodology and sources. The results of the previous parts of the series are used as research tools. The axioms and methods of verb categorization formulated earlier are used to develop the necessary mathematical representations of the verb axiomatics.Results and discussion. The article introduces the axiom for the verbs of the language (the axiom of the verbal cross) and shows that this axiom is related to the categorization axiom (the correctness axiom). Although this connection is not identical, it becomes such with the additional use of the axiom of extensiveness. This relationship made it possible to formulate the fundamental principle of linguistics – the principle of duality.Conclusion. The axiomatics of verbs and categories of a language turns out to be connected, and one determines the other, so that by and large it does not matter which of them is the source of the model of the world and the appearance of language. This unity is formulated as the principle of duality in linguistics. The manifestations of the principle of duality in the language are diverse, but this article focuses on the discussion of the appearance in the language of verbs-processes and adverbs. This transition is considered, starting with obtaining the initial data about the world, to the emergence of ideas about processes and adverbs as a feature system of verbs.

This study is a small-scale action research on the problem of EFL/ESL students' participation in group activities during the crisis of the COVID-19 pandemic. The main stages of the research were conducted in the academic year of 2020/21. The population of the study is twenty-eight Ukrainian secondary school students and three teachers. The research aims at designing a method for ensuring learner engagement in and equal contribution to the group project during distance learning. The methodological basis of this study is the theories of "The Model of Willingness to Communicate", "Collaborative Learning" and "Social Interdependence". The quantitative and qualitative data have been collected through the mixed-method approach, in particular via pedagogical observation, surveys (teacher interviews and student questionnaires), peer evaluation, and mathematical statistics (descriptive and frequency methods). The analysis of scientific pedagogical and psychological literature on student engagement during traditional (in-person) and distance (synchronous and asynchronous) learning, including the use of social networks in education (Viber, Zoom, etc.), helped to identify the main factors that affect learner engagement and equal participation in group activities, such as psychological (self-confidence, anxiety, shyness, and personality), group formation (group size, teacher/student-formed, and homogeneous/heterogeneous), monitoring (self, peer and teacher) and evaluation (peer and teacher). The results of this study demonstrate that the teacher greatly influences the success and equality of student participation in small-group activities. Identifying reasons for unequal participation in the target group of learners, considering students' personality traits and individual needs, and using appropriate planning, organizing and monitoring strategies are the key to their active engagement and effective group work. The results of this study could be used by researchers and practitioners working in the sectors of secondary and tertiary education.

The purpose of the article is to consider the current state and forecast the conjuncture of the domestic apple market, taking into account the seasonality of their sale by all categories of farms. Research methods. The following methods are used in the research: analysis and synthesis, analytical generalizations, graphic - in the analysis of the production and sale of apples by various producers, foreign trade; balance sheet - when determining the market equilibrium of supply and demand, their changes and mutual influence, export and import supplies of fruits; statistical, extrapolation, design and calculation, mathematical modeling, decomposition of the time series - when forecasting the situation and sales volumes, taking into account the seasonality in the domestic apple market. Research results. The principal trends and peculiarities of functioning have been determined, the forecast of the domestic apple market development has been made, and structural changes in their export-import supplies have been established. On the basis of the formed balance of apples, the level of consumer security and expenses of the population was determined. The parameters of forecasting the sales volumes of these fruits by all categories of farms are considered. An economic forecasting model has been built taking into account the seasonal nature of the market. Scientific novelty. Methodical approaches to forecasting the apple market, taking into account the seasonal component, have been further developed, in particular, the optimal periods for forecasting, due to the specifics of the horticulture industry, have been established, which makes it possible to improve the quality and accuracy of the forecast. Practical significance. Taking into account that certain scientific aspects regarding forecasting the market conditions of fruit and berry products are debatable, the forecast of apple sales, taking into account the seasonal component, is an important element of strategic long-term planning for the development of the horticulture industry as part of the national economy. Tabl.: 2. Figs.: 2. Refs.: 15.

Analysis of trade cooperation between countries and identification of the most significant market participants is of great importance, both theoretically and empirically. The global trading community forms a network of international relations defined by trade contracts in various industries. Export-import trade flows are one of the key indicators of the level of cooperation among countries and the state of the global economy. The high intensity of such contacts across groups of countries suggests the existence of clusters in this market segment,consisting of central players — exporters and importers, who often define rules for other participants.Understanding the existence and identification of such a center helps to develop an optimal international trade strategy. The purpose of this contribution is to identify factors affecting trade flows among different countries. Statistical analysis of the international trade relations does not always reveal all the essential aspects of cooperation. This paper combines the methods of graph theory and econometric analysis to study the parameters of trade flows among countries. The parameters used in the network analysis make it possible to obtain additional characteristics of market participants, which help to evaluate their significance in the world trade. The paper also identifies some key mathematical and economic characteristics of export-import flows connecting destination countries. We have analyzed the directions of changes in world trade and established correspondences between metric characteristics of graph vertices and parameters of world trade models. The Russian indicators in export/import categories and its largest sales agents are estimated. The identification of the key intermediaries and importers (centers and authorities) on each of the markets in question has been carried out. As an example for this identification the market of agricultural products among the world's largest exporters and importers of the product were used.

The rapid development of the Internet has had an unprecedented impact on the improvement of the sociological method. At the turn of the millennium, this has led to the search for a new methodology and a gradual loss of interest to use of quantitative methods, which was perceived by specialists as a "crisis of empirical sociology". In the last decade, it turned out that almost all social processes of any level find their reflection in the virtual space, leave and accumulate so-called "digital footprints", which opens to researchers the widest perspectives for study of social reality. This article considers the features of digital primary information and generalized approaches to its use in terms of quantitative methodology. The author emphasizes that the classical sociological methods, which are based on mathematical statistics, are suitable for the analysis of digital reality and getting adequate research results. At the same time, as noted by most authors, who have studied this subject, there are perspectives for improving traditional sociological methods through: 1) a combination of representativeness of quantitative and depth of qualitative approaches to information analysis; 2) in-depth collection of paradata; 3) opportunities to study hard-to-reach social groups; 4) opportunities to fully implement the "principle of freedom from evaluation" due to the "non-reactivity" of digital data; 5) the ordering of digital footprints in space and time by clearly fixing the hosting. The post-demographic model of the social actor opens new ways to build samples of quantitative sociological research, which may be representative in terms of the classical sociological approach. The examples of research from this article show that the classical sociological method easily to adapt for the new digital reality and can be the basis for sociological consulting, development of social technologies in various spheres of social life.

Purpose: to assess the tourism industry development and its impact on Ukraine's economy, to identify a set of problems hindering the significant development of the tourism industry, and to justify ways to increase competitiveness in the world market. Design/Method/Approach of the research: System approach, synthesis, analysis and comparison to assess the tourism development dynamics in Ukraine, correlation and regression analysis to determine the impact level of increasing the number of hotels and tourist-recreational enterprises on GDP growth in Ukraine, logical generalization to identify a set of problems holding back the significant development of local tourism and ways justification of increasing its competitiveness on the world market. Findings: This article presents the results of assessing the tourism dynamics, particularly the tourist flows, the number of resorts, the number of tourists served by tour operators and travel agents. The authors substantiated the ways of increasing the local tourism sector's competitiveness. Practical implications: The work results can make the basis for the development of fundamental and scientific-applied provisions contributing to the significant system formation of increasing the competitiveness of Ukraine's tourism industry by state and local authorities, establishing cooperation among market participants and forming optimal logistics flows, developing business models to optimize the flows of health and recreational facilities. Originality/Value: The research value is that its applied scientific provisions can be implemented in the strategy of economic development of local tourism in analytical and mathematical justifications of the relationship between economic growth and tourism development, which ultimately increases Ukraine regions' competitiveness for sustainable development of the country's economy. Research limitations/Future research. Future research should focus on identifying mechanisms to improve the procedure for increasing tourism enterprises' competitiveness and improving provided service quality. Paper type: empirical.

AbstractIntroductionHIV controllers (HIC) maintain viraemia at low levels without antiretroviral treatment and have small HIV reservoirs. Nevertheless, they are heterogeneous regarding their risk of infection progression. The study of reservoirs can help elucidate this control. This study aimed to explore the factors implicated in the pathogenesis of HIV infection that are potentially associated with HIV reservoirs and their dynamics in HIC.MethodsIndividuals living with HIV included in the ANRS‐CODEX cohort with at least two HIV‐DNA measurements between 2009 and 2016 were selected. The total HIV‐DNA levels had been quantified prospectively from blood samples. Mixed‐effect linear models estimated the HIV‐DNA dynamics over time.ResultsThe median (interquartile range (IQR)) HIV‐DNA level was 1.5 (1.3 to 1.9) log copies/million peripheral blood mononuclear cells at inclusion (n = 202 individuals). These low levels showed heterogeneity among HIC. Lower levels were then associated with the protective HLA‐B*27/B*57 alleles and/or lower HIV‐RNA level at inclusion, negative hepatitis C virus serology, lower HIV‐suppressive capacity of specific CD8 T cells and lower levels of immune activation and inflammation. Interestingly, mathematical modelling of the dynamics of HIV‐DNA over time (840 measurements) showed that the number of infected cells decreased in 46% of HIC (follow‐up: 47.6 months) and increased in 54% of HIC. A multivariate analysis indicated that HLA‐B*27/B*57 alleles, a low level of HIV‐RNA and a low level of HIV‐DNA at inclusion were markers independently associated with this decrease.ConclusionsThese results offer new insights into the mechanisms of long‐term control in HIC. In half of HIC, the decrease in HIV‐DNA level could be linked to tighter viral control and progressive loss of infected cells. These findings allow the identification of HIC with a low risk of progression who may not need treatment.

Purpose– The focus is the interplay of cognitive capabilities (mathematical understanding and heuristic problem solving) and learning from feedback. Furthermore, the authors analyze the role of individual factors in designing appropriate feedback systems for complex decision-making situations. Based on a learning model the purpose of this paper is to present an experimental study analyzing the feedback effectiveness in a repeated complex production planning task. Referring to individual characteristics in terms of educational background and problem solving capabilities of the decision maker the authors compare different forms of feedback systems.Design/methodology/approach– The authors performed four experiments bi-weekly based on a realistic production planning situation. Participants received – depending on the treatment – different types of feedback concerning the final outcomes of the production plans. For testing the hypotheses, the authors conducted ANCOVAs and additionalpost hoctests for each subgroup to explore the effects of different types of feedback on the subgroups' decision-making performance.Findings– The authors show that feedback information is not always helpful, but due to acquired knowledge and problem solving capabilities can even be harmful. The authors also show that, depending on the decision maker's individual characteristics and her past performance, the type of feedback is crucial for the learning process.Practical implications– The study provides important information about feedback design taking individual characteristics of decision makers (educational background, work experience) into account. Applying the results of the study can increase decision-making performance and enhance learning of production planning tasks.Originality/value– The findings extend previous literature reporting that the performance in complex decision-making tasks depends on educational background and on the ability to cope with the phenomena of cognitive load, working memory limitations and the capability to utilize relevant heuristics to prevent information overload. Some of our results, e.g., the negative impact of non-financial feedback of high-performing economists, contradict the general findings in the literature.