Keywords: coefficient of variation function; outlier detection; functional data analysis
The coefficient of the variation function is a useful descriptive statistic, especially when comparing the variability of more than two curve groups, even when they have significantly different mean curves. Since the coefficient of variation function is the ratio of the mean and standard deviation functions, its particular property is that it shows the acceleration more explicitly than the standard deviation function. The aim of the study is twofold: to show that the functional coefficient of variation is more sensitive to abrupt changes than the functional standard deviation and to propose the utilisation of the functional coefficient of variation as an outlier detection tool. Several simulation trials have shown that the coefficient of the variation function allows the effects of outliers to be seen explicitly.
Modelling the volatility of African capital markets in the presence of the Covid-19 pandemic: evidence from five emergingeconomies in Africa
Author(s): Nureni Olawale Adeboye,Sakinat Oluwabukonla Folorunso,Olawale Victor Abimbola,Rasaki Yinka Akinbo / Language(s): English
/ Issue: 2/2023
Keywords: African countries; capital market; COVID-19; volatility; GARCH model
The growing concern over the global effects of the COVID-19 pandemic on every aspect of human endeavour has necessitated a continuous modelling of its impact on socio-economic phenomena, allowing the formulation of policies aimed at sustaining future economic growth and mitigating the looming recession. The study employed Exponential Generalised Autoregressive Conditional Heteroscedasticity (EGARCH) procedures to develop stock volatility models for the pre- and COVID-19 era. The Fixed-Effects Two Stage Least Square (TSLS) technique was utilised to establish an empirical relationship between capital market volatility and the COVID-19 occurrence based on equity market indices and COVID-19 reported cases of five emerging African economies: Nigeria, Egypt, South Africa, Gabon and Tanzania. The stock series was made stationary at the first order differencing and the model results indicated that the stock volatility of all the countries responded sharply to the outbreak of COVID-19 with the average stock returns of Nigeria and Gabon suffering the most shocks. The forecast values indicated a constant trend of volatility shocks for all the countries in the continuous presence of the COVID-19 pandemic. Additionally, the confirmed and death cases of COVID-19 were found to increase stock prices while recovered cases bring about a reduction in the stock prices in the studied periods.
Bayesian estimation of fertility rates under imperfect age
reporting
Author(s): Vivek Verma,Dilip C. Nath,S. N. Dwivedi / Language(s): English
/ Issue: 2/2023
Keywords: Fisher information; square error loss function; age-specific marital fertility rate; Bayes estimator; maximum likelihood principle
This article outlines the application of the Bayesian method of parameter estimation to situations where the probability of age misreporting is high, leading to transfers of an individual from one age group to another. An essential requirement for Bayesian estimation is prior distribution, derived for both perfect and imperfect age reporting. As an alternative to the Bayesian methodology, a classical estimator based on the maximum likelihood principle has also been discussed. Here, the age misreporting probability matrix has been constructed using a performance indicator, which incorporates the relative performance of estimators based on age when reported correctly instead of misreporting. The initial guess of performance indicators can either be empirically or theoretically derived. The method has been illustrated by using data on Empowered Action Group (EAG) states of India from National Family Health Survey-3 (2005–2006) to estimate the total marital fertility rates. The present study reveals through both a simulation and real-life set-up that the Bayesian estimation method has been more promising and reliable in estimating fertility rates, even in situations where age misreporting is higher than in case of classical maximum likelihood estimates.
The prediction of new Covid-19 cases in Poland with machine learning models
Author(s): Adam Chwila / Language(s): English
/ Issue: 2/2023
Keywords: machine learning; time series; COVID-19; forecasting; economic activity
The COVID-19 pandemic has had a huge impact both on the global economy and on everyday life in all countries all over the world. In this paper, we propose several possible machine learning approaches to forecasting new confirmed COVID-19 cases, including the LASSO regression, Gradient Boosted (GB) regression trees, Support Vector Regression (SVR), and Long-Short Term Memory (LSTM) neural network. The above methods are applied in two variants: to the data prepared for the whole Poland and to the data prepared separately for each of the 16 voivodeships (NUTS 2 regions). The learning of all the models has been performed in two variants: with the 5-fold time-series cross-validation as well as with the split into the single train and test subsets. The computations in the study used official statistics from government reports from the period of April 2020 to March 2022. We propose a setup of 16 scenarios of the model selection to detect the model characterized by the best ex-post prediction accuracy. The scenarios differ from each other by the following features: the machine learning model, the method for the hyperparameters selection and the data setup. The most accurate scenario for the LASSO and SVR machine learning approaches is the single train/test dataset split with data for the whole Poland, while in case of the LSTM and GB trees it is the cross validation with data for whole Poland. Among the best scenarios for each model, the most accurate ex-post RMSE is obtained for the SVR. For the model performing best in terms of the ex-post RMSE, the interpretation of the outcome is conducted with the Shapley values. The Shapley values make it possible to present the impact of auxiliary variables in the machine learning model on the actual predicted value. The knowledge regarding factors that have the strongest impact on the number of new infections can help companies to plan their economic activity during turbulent times of pandemics. We propose to identify and compare the most important variables that affect both the train and test datasets of the model.
Informative sampling refers to a sampling design for which the sample selection probabilities depend on the values of the model outcome variable. In such cases the model holding for the sample data is different from the model holding for the population data. Similarly, nonignorable nonresponse refers to a nonresponse mechanism in which the response probability depends on the value of a missing outcome variable. For such a nonresponse mechanism the model holding for the response data is different from the model holding for the population data. In this paper, we study, within a modelling framework, the semi-parametric prediction of a finite population total by specifying the probability distribution of the response units under informative sampling and nonignorable nonresponse. This is the most general situation in surveys and other combinations of sampling informativeness and response mechanisms can be considered as special cases. Furthermore, based on the relationship between response distribution and population distribution, we introduce a new measure of the representativeness of a response set and a new test of nonignorable nonresponse and informative sampling, jointly. Finally, a calibration estimator is obtained when the sampling design is informative and the nonresponse mechanism is nonignorable.
Author(s): Zofia Zielińska-Kolasińska,Wojciech Zieliński / Language(s): English
/ Issue: 2/2023
Keywords: confidence interval; odds ratio
We consider the problem of interval estimation of the odds ratio. An asymptotic confidence interval is widely applied in economics, medicine, sociology, etc. Unfortunately, this confidence interval has a poor coverage probability, significantly smaller than the nominal confidence level. In this paper, a new confidence interval is proposed. Its construction requires only information on the sizes of samples and the sample odds ratio. The coverage probability of the proposed confidence interval is at least the nominal confidence level.
Determinants of livestock products export in Ethiopia
Author(s): Ermyas Kefelegn / Language(s): English
/ Issue: 2/2023
Keywords: livestock export; VAR; VECM
Ethiopia has one of the largest livestock populations in Africa. In 2016–2017, the share of live animals, leather, and meat in the total export of the country reached 9.6%. This paper aims to identify the determinants of the export of Ethiopian livestock products by means of vector autoregressive and vector error correction models. Multivariate time series is used to model the association between the products of the Ethiopian livestock export included in the study. Vector autoregressive and vector error correction models are used for modelling and inference. The results indicated the existence of a long term correlation between the volume of live animals, meat and leather exports. The volume of meat export is significantly affected by a lag occurring in the export of live animals in the short-run. Therefore, 3.7% of the shortrun imbalance in the volume of leather export is adjusted each quarter. It is suggested that the exporters of livestock products should properly utilise the Ethiopian livestock resources. On the other hand, the government should offer different forms of support to exporters, especially those focusing on exporting value-added produc
On some efficient classes of estimators using auxiliary attribute
Author(s): Shashi Bhushan,Anoop Kumar / Language(s): English
/ Issue: 2/2023
Keywords: Bias; Mean square error; Efficiency; Auxiliary attribute
This paper considers some efficient classes of estimators for the estimation of population mean using known population proportion. The usual mean estimator, classical ratio, and regression estimators suggested by Naik and Gupta (1996) and Abd-Elfattah et al. (2010) estimators are identified as the members of the suggested class of estimators. The expressions of bias and mean square errors are derived up to first-order approximation. The proposed estimators were put to test against various other competing estimators till date. It has been found both theoretically and empirically that the suggested classes of estimators dominate the existing estimators.
Proposal of a causal model measuring the impact of an ISO 9001 certified Quality Management System on financial performance of Moroccan service-based companies
Author(s): El Moury Ibtissam,Mohamed Hadini,Adil Chebir,Ben Ali Mohamed,Echchelh Adil / Language(s): English
/ Issue: 2/2023
Keywords: financial performance; organisational performance; Quality Management System (QMS); ISO 9001 certification
Implemented by an increasing number of organisations worldwide, the ISO 9001 standard for quality management received considerable attention in the existing literature. Researchers worldwide have found positive, negative and even mixed effects of ISO 9001 certification on firms’ performance, while in Morocco this issue has been rarely examined. It is the combination of these observations that led to this study. The aim of this paper is to test and validate a causal model designed to measure the performance of an ISO 9001 certified Quality Management System (QMS) and its impact on a company’s financial performance. By means of this causal analysis/model, the study examines the relationship between: • QMS and the financial performance of 41 companies based in Morocco; • the management responsibility process and all the QMS processes; • the management resources process and all the QMS processes; • the organisational and financial performance of the studied companies. All of the considered firms are part of the service industry and range from medium-sized to large companies. The data gathered in this study have been instrumental in devising actionable insights. The Statistical Package for the Social Sciences (SPSS) was the statistical software platform that enabled the use of a linear regression analysis to prove the positive correlation between the above-mentioned elements.
Dynamics of survey responses before and during the pandemic: entropy and dissimilarity measures applied to business tendency survey data
Author(s): Emilia Tomczyk / Language(s): English
/ Issue: 2/2023
Keywords: business cycles; survey data; expectations; manufacturing industry; COVID-19 pandemic
This article is set within the framework of studies focusing on the impact of the SARS-CoV-2 virus on the dynamics of economic activity. For the purposes of the analysis of the expectations expressed in business tendency surveys, the paper aims to verify whether the pandemic of 2020-2022 can be seen as just another contraction phase. Entropy and dissimilarity measures are employed to study the characteristics of the expectations and assessments expressed in the business tendency survey of Polish manufacturing companies. The empirical results show that the dynamics of the manufacturing sector data, particularly as far as general economic conditions are concerned, set the pandemic period apart. The economic consequences of the COVID-19 pandemic expressed in business tendency surveys tend to be unfavourable, but the statistical properties or the degree of the concentration of respondents’ answers do not correspond closely either to the expansion or contraction phases of the business cycle
Breaking Benford’s law: a statistical analysis of COVID-19 data using the Euclidean distance statistic
Author(s): Leonardo Campanelli / Language(s): English
/ Issue: 2/2023
Keywords: Benford’s law; COVID-19 data
Using the Euclidean distance statistical test of Benford’s law, we analyse the COVID-19 weekly case counts by country. While 62% of the 100 countries and territories considered in the present study conforms to Benford’s law at a significant level of α = 0.05 and 17% at a significant level of 0.01 ≤ α < 0.05, the remaining 21% shows a deviation from it (p values smaller than 0.01). In particular, 5% of the countries ‘break’ Benford’s law with a p value smaller than 0.001.
HOW TO RESOLVE THE TERRITORIAL
CONFLICTS IN UKRAINE: UTI POSSIDETIS
JURIS AND AN INTERNATIONAL LAW-BASED
PROPOSAL FOR POWER-SHARING
Author(s): Tero Lundstedt / Language(s): English
/ Issue: 41/2021
Keywords: international law; Russia; Ukraine; Crimea; territorial conflicts
In this article, I present a proposal for an international law-based formula for mediating territorial conflicts and apply it to the case of Crimea in Ukraine.Although the tragic Russian attack which commenced on 24 February 2022 has made the mediation even more difficult, once a ceasefire is achieved my formula is capable of providing legally solid compromises to the Ukrainian territorial questions that fit into the contemporary international legal framework concerning territory.Naturally, any realistic solution will require concessions on the part of all stakeholders(primarily Crimea, Ukraine, and Russia). In short, the formula offers for Ukraine the return of its territorial integrity, for Crimea internal self-determination in the form of a meaningful territorial autonomy, and for Russia a few indirect perks and guarantees, mostly related to a possible demilitarization of the Crimean Peninsula.The analysis can also be useful for Donbas, for which the formula offers recognition of some limited autonomous rights.
PUSHBACKS IN POLAND: GROUNDING
THE PRACTICE IN DOMESTIC LAW IN 2021
Author(s): Grażyna Baranowska / Language(s): English
/ Issue: 41/2021
Keywords: pushbacks; border violence; asylum; international protection; pro- hibition of collective expulsions
In the summer of 2021 deliberate actions by the Belarusian state authorities led to a huge increase of people irregularly crossing the border from Belarus to Poland.Instead of addressing this humanitarian crisis, the Polish government responded with actions that were in violation of its international obligations and domestic law.Among these measures was carrying out “pushbacks” and grounding them in Polish domestic law. “Pushbacks” are the practice of returning people to the border without assessing their individual situation. The formalization of those practices in 2021 was done within two legal frameworks; one interim and one permanent. They continue to function in parallel while containing different provisions. This article assesses the two frameworks’ compatibility with domestic and international law and concludes that they both violate domestic and international rules. In the context of EU law,the article demonstrates the incompatibility of the two frameworks with the so-called Asylum Procedures Directive and Return Directive. The article further argues that the pushbacks violate the European Convention of Human Rights and would not fall within the exceptions to the prohibition of collective expulsions.
THE MISSING POST-HOLOCAUST TRACES
IN RECENT CASE LAW OF THE EUROPEAN
COURTS
Author(s): Aleksandra Gliszczyńska-Grabias / Language(s): English
/ Issue: 41/2021
Keywords: Holocaust; boycotts; ritual slaughter bans; anti-discrimination law; religious freedom
The Holocaust constitutes one of the most powerful symbols in the history of humankind. Its memory, and in particular its irrefutable relationship with anti-Semitism, should trigger strict scrutiny every time anti-Semitic attitudes re-emerge, even if disguised as seemingly harmless words or actions. This applies also to legal measures,neutral on their face but which, in their consequences, may have an adverse effect on Jews, and thus raise the suspicion of anti-Semitic implications. Such implications are visible in the recent phenomena that serve as the two case studies for the present article:boycotts of Israel and bans on ritual slaughter (Shechita). While in the case of anti-Israeli boycotts, the core arguments relate to international anti-discrimination law and policies, in relations to the Shechita bans claims about violation of the religiousfreedom of observant Jews prevail. At the same time, in both cases strong references to the Holocaust and the memory of its victims are being invoked, allowing one to raise objections as to the status of the relevant legal developments. Here again history and memory enter into the public and legal discussions, legislative processes, and courtrooms.
SPECIAL JURISDICTION IN INFRINGEMENTS
OF PERSONALITY RIGHTS
Author(s): Marek Świerczyński,Remigijus Jokubauskas / Language(s): English
/ Issue: 41/2021
Keywords: special jurisdiction; personality rights; Brussel I bis; torts; Internet
This article focuses on the problems of jurisdiction in cross-border civil proceedings concerning an alleged violation of personality rights. There are no specific rules on jurisdiction for such torts in European Union law. In the current case law of the Court of Justice of the European Union (CJEU), Art. 7(2) of the Brussels I bis Regulation is applicable to such disputes. Nevertheless, the authors argue that the CJEU has misinterpreted this article when the claim is based on violation of personality rights, and has thus created a legal chaos in such disputes. The authors analyse the peculiarities of Internet infringements and the locus delicti connecting factor in the case law of the CJEU in this area. The Court has adopted the criterion of ‘centre of interests’ as the major connecting factor to establish international jurisdiction. The authors criticize this approach and argue that it has led to a structural misunderstanding of the infringement of personality rights. Finally, the authors propose a new rule on jurisdiction in cases concerning violation of personality rights, which should be established in the Brussels I bis Regulation to ensure legal certainty and proper international dispute settlement.
Valérie V. Suhr, Rainbow Jurisdiction at the
International Criminal Court. Protection of Sexual
and Gender Minorities Under the Rome Statute,
T.M.C. Asser Press, Springer: 2022, pp. 405
Author(s): Hanna Kuczyńska / Language(s): English
/ Issue: 41/2021
Da Revolução dos Cravos à independência de Angola – receção na imprensa polaca. O caso do semanário informativo "Polityka" (1974-1976)
Author(s): Anna Działak-Szubińska / Language(s): English
/ Issue: 34/2021
Keywords: Polityka; Polish press in the ‘70; the independence of Angola; the Carnation Revolution; decolonization of Africa
This article presents the Polish press’ reception of the Carnation Revolution and, as coming in its aftermath – the decolonization of Africa till the independence of Angola, on the basis of texts published in the weekly news magazine Polityka (years 1974-1976). The analysis encapsulates both more exhaustive articles and shorter notes from the international section (“Za granicą”). The research, by shedding light on political predilections of contemporary Poland, illuminates how the interest in the Carnation Revolution translates into the readings of decolonization- related topics in the form of reportages, essays, interviews, among others.
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