Browsing by Author "Omay, Tolga"
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Article A long‑run convergence analysis of aerosol precursors, reactive gases, and aerosols in the BRICS and Indonesia: is a global emissions abatement agenda supported?(Environmental Science and Pollution Research, 2023-02) Romero‑Ávila, Diego; Omay, TolgaThis article examines the hypothesis of deterministic emissions convergence for a panel of the BRICS and Indonesia to advanced countries’ emissions levels as well as to Sweden (which is a country that has clearly gone through decoupling) using a novel dataset with ten series of annual estimates of anthropogenic emissions comprising aerosols, aerosol precursor and reactive compounds, and carbon dioxide from 1820 to 2018. For that purpose, we employ four novel panel unit root tests allowing for several forms of time-dependent and state-dependent nonlinearity. The evidence supports deterministic convergence following a linear process for carbon dioxide, whereas the adjustment is asymmetric and nonlinear for carbon monoxide. Methane and nitrogen oxides exhibit logistic smooth transition converging dynamics. In contrast, black carbon, ammonia, nitrous oxide, non-methane volatile organic compounds, organic carbon, and sulfur dioxide emissions diverge. These results have implications for the abatement of greenhouse gases emissions at the global level, given the high share of emissions of the BRICS.Article A note on CO2 emissions using two new tests(Empirica, 2023-11) Sephton, Peter; Omay, TolgaRecent research suggests that policies implementing structural change are required to alter the paths of carbon dioxide emissions in many nations. This note provides additional support for this view, allowing for smooth shifts in the deterministic part of the stochastic process. A Fourier wavelet unit root test indicates that in many countries, a temporary shock to emissions will have a permanent impact, whereas tests that examine fractional integration around a smooth break with de-trending indicate that a shock to emissions will have a transitory impact. Policies that induce structural changes are required to place emissions on a downward path.Article Controlling Heterogeneous Structure of Smooth Breaks in Panel Unit Root and Cointegration Testing(Computational Economics, 2023-01) Omay, Tolga; Iren, PerihanThis study aims to show the consequences of a restrictive homogeneity assumption of frequency in heterogeneous panel unit root and cointegration testing with Flexible Fourier Form. For this purpose, we use a simple panel unit root and residual based cointegration test with Flexible Fourier Form in a heterogeneous frequency setting using a bootstrap algorithm. The power of the test statistics and empirical analysis results indicate that failing to take into account a heterogeneous frequency may lead to misleading inferences, thereby leading to misspecified tests and erroneous conclusions concerning the stochastic behavior of the data in the panel sample.Article Convergence of economic growth and health expenditures in OECD countries: Evidence from non-linear unit root tests(Frontiers in Public Health, 2023-03-17) Çelik, Eşref Uğur; Omay, Tolga; Tengilimoğlu, DilaverIntroduction: The relationship between human capital, health spending, and economic growth is frequently neglected in the literature. However, one of the main determinants of human capital is health expenditures, where human capital is one of the driving forces of growth. Consequently, health expenditures affect growth through this link. Methods: In the study, these findings have been attempted to be empirically tested. Along this axis, health expenditure per qualified worker was chosen as an indicator of health expenditure, and output per qualified worker was chosen as an indicator of economic growth. The variables were treated with the convergence hypothesis. Due to the non-linear nature of the variables, the convergence hypothesis was carried out with non-linear unit root tests. Results: The analysis of 22 OECD countries from 1976 to 2020 showed that health expenditure converged for all countries, and there was a significant degree of growth convergence (except for two countries). These findings show that health expenditure convergence has significantly contributed to growth convergence. Discussion: Policymakers should consider the inclusiveness and effectiveness of health policies while making their economic policies, as health expenditure convergence can significantly impact growth convergence. Further research is needed to understand the mechanisms behind this relationship and identify specific health policies most effective in promoting economic growth.Article Convergence of GHGs emissions in the long‑run: aerosol precursors, reactive gases and aerosols—a nonlinear panel approach(Environment, Development and Sustainability, 2023-11) Romero‑Ávila, Diego; Omay, TolgaAnthropogenic emissions of reactive gases, aerosols and aerosol precursor compounds are responsible for the ozone hole, global warming and climate change, which have altered ecosystems and worsened human health. Environmental authorities worldwide have responded to these climate challenges through the 2030 Agenda for Sustainable Development. In this context, it is key to ascertain empirically whether emission levels are converging among the countries forming the industrialized world. In doing so, we focus on 23 industrialized countries using a novel dataset with ten series of annual estimates of anthropogenic emissions that include aerosols, aerosol precursor and reactive compounds, and carbon dioxide over the 1820–2018 period. We apply four state-of-the-art panel unit root tests that allow for several forms of time-dependent and state-dependent nonlinearity. Our evidence supports stochastic convergence following a linear process for carbon dioxide, whereas the adjustment is nonlinear for black carbon, carbon monoxide, methane, non-methane volatile organic compounds, nitrous oxide, nitrogen oxides and sulfur dioxide. In contrast, ammonia and organic carbon emissions appear to diverge. As for deterministic convergence, carbon dioxide converges linearly, while black carbon, carbon monoxide, nitrogen oxides, non-methane volatile organic compounds and sulfur dioxide adjust nonlinearly. Our results carry important policy implications concerning the achievement of SDG13 of the global 2030 Agenda for Sustainable Development, which appears to be feasible for the converging compounds.Article How Does Macroeconomic and Socio-political Index Affect the Real GDP per Qualified Worker? Evidence from Turkish Republics(Bilig, 2023-04-27) Çelik, Eşref Uğur; Erdal, Fehmi Buğra; Küçüker, Mustafa Can; Omay, TolgaIn this study, we concentrated on the socioeconomic factors affecting the level of real GDP per qualified worker. For this purpose, we have used the macroeconomic and socio-political performance index for Turkish Republics. By using these newly established indices, determinants of the level of real GDP per qualified worker are analyzed for the first time in the literature. From the empirical investigation, we found that certain threshold levels significantly affect the real GDP level per qualified worker. Therefore, the policymakers of these countries have to seriously consider these threshold levels for macroeconomic and socio-political performance index for conducting a well-organized policy for the wellbeing of their countries.Article Is there convergence in renewable energy deployment? Evidence from a new panel unit root test with smooth and sharp structural breaks(Renewable Energy, 2023-03) Çorakçı, Ayşegül; Omay, TolgaThis study examines whether the contribution of renewable energy to the total primary energy supply converges in a panel of 24 OECD countries over the period 1960–2020. To this end, a new panel unit root test that allows for both sharp and smooth breaks is proposed to test for the stochastic convergence hypothesis. Although renewable energy convergence is not rejected when the newly proposed test is applied to the full panel of OECD countries, it found only moderate support within the members of the panel using a sequential panel selection methodology. In fact, in two high-income OECD countries, the contribution of renewable energy to the primary energy supply shows no sign of convergence: Poland and Iceland. Therefore, the renewable energy shares seem to be converging to a common steady state in only a group of OECD countries over the long run. This uneven pattern of convergence, in turn, suggests that the OECD countries are still far away from developing a common sustainable renewable energy target, calling for urgent international policy cooperation to encourage the divergent economies to seek out the menu of policies that ensure the worldwide success of renewable energy transformation.Item KÜRESEL LİKİDİTE KOŞULLARININ BORSA İSTANBUL ENDEKSLERİNE ETKİLERİ(2022-01-18) Altuntaş, Canan Özlem; Omay, TolgaKüreselleşme ve finansal serbestleşmenin bir sonucu olarak, bir ülkenin finansal piyasasında yaşanan bir değişiklik yerel bir etkiyle sınırlı kalmamakta, diğer finansal piyasalara da yayılmaktadır. Bu tez çalışmasında, küresel likidite koşullarının Borsa İstanbul üzerindeki etkilerinin analiz edilmesi amaçlanmıştır. Bu kapsamda, 01.01.2010 – 31.03.2020 tarihleri arası BIST 100 endeksi log-getirileri ile VIX endeksinin günlük kapanış verileri, bir Çok Değişkenli GARCH model spesifikasyonu olan Sabit Koşullu Korelasyon GARCH (CCC-GARCH) yöntemi ve Gecikmesi Dağıtılmış Otoregresif (ARDL) model kullanılarak analiz edilmiştir. Çalışmada VIX endeksi, global likiditeyi temsilen vekil değişken olarak kullanılmıştır. Elde edilen ampirik sonuçlar, beklentilerle paralel olarak VIX ve BIST 100 endeksleri arasında negatif korelasyon olduğu, BIST 100 endeksinin küresel finansal piyasalarla tam entegre olduğu ve dolayısıyla küresel likidite koşullarında meydana gelen bir şokun BIST 100 endeksini de etkilediği yönündedir.Article Phase and wave dependent analysis of health expenditure efficiency: A sample of OECD evidence(Frontiers in Public Health, 2023-03-17) Boduroğlu, Elif; Atıcı, Kazım Barış; Omay, TolgaIntroduction: Health expenditures are a factor that reflects the government's public health policy and contributes to the protection of national health. Therefore, this study focuses on measuring the effectiveness of health expenditures in order to evaluate and improve the public health system and policy during the pandemic period. Method: In order to examine the effectiveness of health expenditures, the behaviors of the pandemic process were analyzed in two stages. The number of daily cases is analyzed in the first stage by dividing it into waves and phases according to the transmission coefficient (R). For this classification, the discrete cumulative Fourier function estimation is used. In the second stage, the unit root test method was used to estimate the stationarity of the number of cases in order to examine whether the countries made effective health expenditures according to waves and phases. The series being stationary indicates that the cases are predictable and that health expenditure is efficient. Data consists of daily cases from February 2020 to November 2021 for 5 OECD countries. Conclusion: The general results are shown that cases cannot be predicted, especially in the first stage of the pandemic. In the relaxation phase and at the beginning of the second wave, the countries that were seriously affected by the epidemic started to control the number of cas es by taking adequate measures, thus increasing the efficiency of their health systems. The common feature of all the countries we examined is that phase 1, which represents the beginning of the waves, is not stationary. After the waves fade, it can be concluded that the stationary number of health cases cannot be sustainable in preventing new waves' formation. It is seen that countries cannot make effective health expenditures for each wave and stage. According to these findings, the periods in which countries made effective health expenditures during the pandemic are shown. Discussion: The study aims to help countries make effective short- and long-term decisions about pandemics. The research provides a view of the effectiveness of health expenditures on the number of cases per day in 5 OECD countries during the COVID-19 Pandemic.Article Testing for Unit Roots in Nonlinear Dynamic Heterogeneous Panels with Logistic Smooth Breaks(Symmetry, 2023-03-18) Omay, Tolga; Uçar, NuriIn this study, we investigate the validity of the purchasing power parity (PPP) proposition for 34 European and selected global countries. For this purpose, we propose a new unit root test for cross-sectionally dependent heterogeneous panels that allows for gradual structural breaks and symmetric nonlinear adjustment toward the equilibrium level. The alternative hypothesis stationary is obtained by symmetric adjustment due to exponential smooth transition autoregression (ESTAR) around a nonlinear trend. Moreover, we provide small sample properties extensively for the newly proposed test. Hence, this alternative hypothesis has been proven to characterize real exchange rate data (REER) correctly. Thus, the newly proposed tests provide an essential basis for modeling the REER series correctly. Finally, we also derive the approximate asymptotic distribution of the proposed tests using new techniques.Article Testing the Efficiency of Emerging Markets: Evidence from Nonlinear Panel Unit Tests(Panoeconomicus, 2023) Turguttopbaş, Neslihan; Omay, TolgaIn this study, we investigate market efficiency considering nonlinearities by testing the weak-form market efficiency of the stock markets of Brazil, China, Russia, Turkey, and South Africa using recently proposed nonlinear panel unit root tests. The stock markets of these emerging countries are deliberately selected for their market capitalization to form a homogenous panel. The results of nonlinear models indicate that the stock market indexes are stationary and weak-form inefficient. This finding contributes to the contradictory results of the prior research using linear and nonlinear models about the efficiency of emerging stock markets in favor of nonlinear ones. Furthermore, we propose that studies using financial variables consider such nonlinearity in order to achieve more accuracy in findings related to such studies.