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Reserves, prices, and policy: an empirical analysis of strategic crop reserves in Arab nations / Rezerwy, ceny i polityka: empiryczna analiza strategicznych rezerw upraw w krajach arabskich
No full textSubject and purpose of work: In recent years, global food systems have faced challenges like disasters, extreme
weather events, and market fluctuations, such as the Ukraine-Russia conflict. This study analyses strategic crop
reserves, specifically for wheat and rice, in Arab countries. It examines the objectives and obstacles associated
with these reserves.
Material and methods: different statistical methods have been used, including regression analysis and neural
network prediction models.
Results: Findings reveal significant agricultural production deficits in Arab economies. However, some countries
maintain substantial crop reserves. We found an inverse relationship between wheat reserves and wheat prices.
Additionally, energy prices correlate positively with agricultural commodity prices. Forecasting models anticipate
short-term global grain stock stability but predict short-term increases in agricultural price indices (until 2024)
followed by long-term decreases (by 2030).
Conclusions: Policymakers should support agricultural strategies, particularly for strategic crops. To address
current challenges, we suggest securing long-term contracts for strategic crops, diversifying suppliers, and
avoiding reliance on a few sources.Przedmiot i cel pracy: W ostatnich latach globalne systemy żywnościowe stanęły w obliczu wyzwań, takich jak
katastrofy, ekstremalne zjawiska pogodowe i wahania rynkowe, np. takie jak konflikt między Ukrainą a Rosją.
Niniejsze badanie analizuje strategiczne rezerwy upraw, w szczególności pszenicy i ryżu, w krajach arabskich.
Badane są cele i przeszkody związane z tymi rezerwami.
Materiały i metody: Zastosowano różne metody statystyczne, w tym analizę regresji i modele predykcyjne sieci
neuronowych.
Wyniki: Wyniki wskazują na znaczne deficyty produkcji rolnej w gospodarkach arabskich. Niektóre kraje
utrzymują jednak znaczne rezerwy upraw. Stwierdzono odwrotną zależność między rezerwami pszenicy a jej cenami.
Co więcej, ceny energii korelują dodatnio z cenami towarów rolnych. Modele prognostyczne przewidują
krótkoterminową stabilność światowych zapasów zbóż, jak również krótkoterminowe wzrosty wskaźników cen
rolnych (do 2024 r.), a następnie długoterminowe spadki (do 2030 r.).
Wnioski: Decydenci polityczni powinni wspierać strategie rolne, szczególnie w odniesieniu do upraw strategicznych.
Aby sprostać obecnym wyzwaniom, sugeruje się zabezpieczenie długoterminowych kontraktów na strategiczne
uprawy, dywersyfikację dostawców i unikanie polegania na kilku źródłach
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Modele prognostyczne oparte na logice rozmytej: aplikacja dotycząca międzynarodowych cen kawy
No full textIn recent decades, Fuzzy Time Series (FTS) has become a competitive, sometimes complementary, approach to classical time series methods such as that of Box-Jenkins. This study has two different purposes: a theoretical purpose, presenting an overview of the fuzzy logic and fuzzy time series models, and a practical purpose, which is to estimate and forecast monthly international coffee prices during the period 2000-2022. Analysing and forecasting the dynamics of coffee prices is of great interest to producers, consumers, and other market actors in managing and making rational decisions. The findings showed that international coffee prices exhibited significant fluctuations, with large increases and decreases influenced mainly by the level of top-ranked producers. The forecasted results revealed that a decrease in prices during the next six months (Jan 2023 to June 2023) is expected. Based on the results, it is also clear that the FTS models are more flexible and can be applied in forecasting time-series variables. At the same time, volatility and, sometimes, the unexpected swingsin coffee prices continue to draw more criticism and raise different issues regarding the roles of the markets and countries in ensuring food security.W ostatnich dziesięcioleciach rozmyte szeregi czasowe stały się konkurencyjnym, czasem uzupełniającym, podejściem wobec klasycznych metod analizy szeregów czasowych, takich jak metoda Boxa-Jenkinsa. Prezentowane badanie ma dwa różne cele: cel teoretyczny, w którym przedstawiono przegląd logiki rozmytej i modeli rozmytych szeregów czasowych, oraz cel praktyczny, którym jest oszacowanie i prognoza miesięcznych międzynarodowych cen kawy w okresie 2000-2022. Analiza i prognozowanie dynamiki cen kawy ma duże znaczenie dla producentów, konsumentów i uczestników rynku w zarządzaniu i podejmowaniu racjonalnych decyzji. Wyniki pokazały, że międzynarodowe ceny kawy wykazywały duże wahania, z dużymi wzrostami i spadkami, na które wpływ miał głównie poziom czołowych producentów. Zgodnie z wynikami prognoz należy spodziewać się spadku cen w ciągu najbliższych sześciu miesięcy (od stycznia do czerwca 2023 r.). Na podstawie uzyskanych wyników można stwierdzić, że modele FTS są bardziej elastyczne i mogą być stosowane w prognozowaniu zmiennych szeregów czasowych. Z drugiej strony zmienność, a czasami nieoczekiwane zmiany cen kawy nadal powodują coraz większą krytykę i sygnalizują, że należy zwrócić uwagę na różne kwestie dotyczące roli rynków i państw w zapewnianiu bezpieczeństwa żywnościowego
Rethinking Scale in Applied Econometrics: Practical Impacts of Log Transformations on Model Performance
Get PDFAim: This study examines the practical impact of measurement scale choices, particularly logarithmic transformations, on the accuracy, reliability, and interpretability of econometric models using macroeconomic indicators from the MENA region.
Methodology: Using real-world MENA data, multiple techniques (OLS, Fixed Effects, Random Effects, GMM) were applied with both raw and log-transformed variables to compare outcomes for variance stability, normality, stationarity, and heteroskedasticity.
Results: Log transformations substantially improve model diagnostics by stabilising variance, enhancing normality, and reducing heteroskedasticity, yielding more precise estimates. However, they alter coefficient interpretation, highlighting a trade-off between statistical robustness and economic meaning.
Implications and Recommendations: The findings underscore the critical need for appropriate data transformations to ensure valid and interpretable results, offering practical guidance for researchers and policymakers in model specification for policy analysis and forecasting.
Originality/Value: This study provides a novel comparative exploration of transformation effects across methodologies and one of the few region-specific investigations using MENA data, delivering actionable insights for methodological and applied research
Determinants of the Age at First Marriage among the University Teachers in Algeria: A mix Methodology Approach
Get PDFThis study examines the determinants of age at first marriage among the university teachers in Algeria. A Weibull proportional hazard and multivariable logistic regressions models were used on data set from a survey covering a sample of 682 teachers. The findings revealed that: The median ages at first marriage are: 36 and 39.4 years for men and women, respectively, with a gap of 3.1 and 8 years from the general population. For: birth order, teacher specialty, study place and working before joining the academic staff all together explain a very small percent of the variation of the age at marriage; in contrast, Housing, salaries’ level, and a suitable partner were the hidden factors determining the age at marriage. As policy implications, policy-makers have to focus on these factors in order to help teachers to satisfy this biological and sociological need.
JEL Classification: C4; J1
Forecasting Models Based on Fuzzy Logic: An Application on International Coffee Prices
No full textIn recent decades, Fuzzy Time Series (FTS) has become a competitive, sometimes complementary, approach to classical time series methods such as that of Box-Jenkins. This study has two different purposes: a theoretical purpose, presenting an overview of the fuzzy logic and fuzzy time series models, and a practical purpose, which is to estimate and forecast monthly international coffee prices during the period 2000-2022. Analysing and forecasting the dynamics of coffee prices is of great interest to producers, consumers, and other market actors in managing and making rational decisions. The findings showed that international coffee prices exhibited significant fluctuations, with large increases and decreases influenced mainly by the level of top-ranked producers. The forecasted results revealed that a decrease in prices during the next six months (Jan 2023 to June 2023) is expected. Based on the results, it is also clear that the FTS models are more flexible and can be applied in forecasting time-series variables. At the same time, volatility and, sometimes, the unexpected swingsin coffee prices continue to draw more criticism and raise different issues regarding the roles of the markets and countries in ensuring food security.(original abstract)W ostatnich dziesięcioleciach rozmyte szeregi czasowe stały się konkurencyjnym, czasem uzupełniającym, podejściem wobec klasycznych metod analizy szeregów czasowych, takich jak metoda Boxa-Jenkinsa. Prezentowane badanie ma dwa różne cele: cel teoretyczny, w którym przedstawiono przegląd logiki rozmytej i modeli rozmytych szeregów czasowych, oraz cel praktyczny, którym jest oszacowanie i prognoza miesięcznych międzynarodowych cen kawy w okresie 2000-2022. Analiza i prognozowanie dynamiki cen kawy ma duże znaczenie dla producentów, konsumentów i uczestników rynku w zarządzaniu i podejmowaniu racjonalnych decyzji. Wyniki pokazały, że międzynarodowe ceny kawy wykazywały duże wahania, z dużymi wzrostami i spadkami, na które wpływ miał głównie poziom czołowych producentów. Zgodnie z wynikami prognoz należy spodziewać się spadku cen w ciągu najbliższych sześciu miesięcy (od stycznia do czerwca 2023 r.). Na podstawie uzyskanych wyników można stwierdzić, że modele FTS są bardziej elastyczne i mogą być stosowane w prognozowaniu zmiennych szeregów czasowych. Z drugiej strony zmienność, a czasami nie-oczekiwane zmiany cen kawy nadal powodują coraz większą krytykę i sygnalizują, że należy zwrócić uwagę na różne kwestie dotyczące roli rynków i państw w zapewnianiu bezpieczeństwa żywnościowego.(abstrakt oryginalny
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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