Omay, Tolga
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T.,Omay
Omay, Tolga
O., Tolga
Tolga, Omay
Omay,T.
O.,Tolga
T., Omay
Omay T.
Omay, Tolga
O., Tolga
Tolga, Omay
Omay,T.
O.,Tolga
T., Omay
Omay T.
Job Title
Profesor Doktor
Email Address
tolga.omay@atilim.edu.tr
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Scholarly Output
51
Articles
46
Citation Count
309
Supervised Theses
2
51 results
Scholarly Output Search Results
Now showing 1 - 10 of 51
Article Citation Count: 17Using Double Frequency in Fourier Dickey-Fuller Unit Root Test(Springer, 2022) Omay, Tolga; Omay, Tolga; EconomicsWe propose a double frequency fourier Dickey-Fuller (DF) unit root test. The asymptotic theory of the newly proposed test is first presented in this study. We conduct a series of simulations which suggest the proposed test statistic has correct size performance and gains more power when breaks are located at the beginning and end of the sample and in smooth type. In empirical analysis, we utilize the new test to examine the unit root hypothesis of relative commodity prices measured by Harvey et al. (Rev Econ Stat 92(2):367-377, 2010). The empirical results show that more relative commodity prices are stationary around a deterministic trend generated from double frequency Fourier function.Article Citation Count: 2Are CO2 Emissions Stationary After All? New Evidence from Nonlinear Unit Root Tests(Springer, 2022) Omay, Tolga; Omay, Tolga; EconomicsThis study applies a large battery of state-of-the-art nonlinear unit root tests to examine the stationarity properties of carbon dioxide emission series for 28 industrialized countries, five BRICS and seven transition economies over a very long horizon, in some cases over more than two and a half centuries. The application of time-dependent and state-dependent nonlinear unit root tests separately provides mixed evidence regarding the time-series properties of CO2 emissions and a high degree of variability across the different tests. However, the use of hybrid nonlinear unit root tests, combining the presence of structural breaks with symmetric or asymmetric ESTAR adjustment, leads to the rejection of the unit root hypothesis in each of the countries under study with at least one of the hybrid tests. This has important climate policy implications.Article Citation Count: 0How Does Macroeconomic and Socio-political Index Affect the Real GDP per Qualified Worker? Evidence from Turkic Republics(Ahmet Yesevi Univ, 2023) Omay, Tolga; Erdal, Fehmi Bugra; Çelik, Eşref Uğur; Erdal, Fehmi Buğra; Küçüker, Mustafa Can; Economics; Tourism ManagementIn 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 Turkic 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 should seriously consider these threshold levels for macroeconomic and socio-political performance index for conducting a well-organized policy for the prosperity of their countries.Article Citation Count: 1Convergence of GHGs emissions in the long-run: aerosol precursors, reactive gases and aerosols-a nonlinear panel approach(Springer, 2023) Omay, Tolga; Omay, Tolga; EconomicsAnthropogenic 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 Citation Count: 11Smooth Break Detection and De-Trending in Unit Root Testing(Mdpi, 2021) Omay, Tolga; Omay, Tolga; Shahzad, Syed Jawad Hussain; Nor, Safwan Mohd; EconomicsThis study explores the methods to de-trend the smooth structural break processes while conducting the unit root tests. The two most commonly applied approaches for modelling smooth structural breaks namely the smooth transition and the Fourier functions are considered. We perform a sequence of power comparisons among alternative unit root tests that accommodate smooth or sharp structural breaks. The power experiments demonstrate that the unit root tests utilizing the Fourier function lead to unexpected results. Furthermore, through simulation studies, we investigate the source of such unexpected outcomes. Moreover, we provide the asymptotic distribution of two recently proposed unit root tests, namely Fourier-Augmented Dickey-Fuller (FADF) and Fourier-Kapetanios, Shin and Shell (FKSS), which are not given in the original studies. Lastly, we find that the selection of de-trending function is pivotal for unit root testing with structural breaks.Article Citation Count: 0Can governments sleep more soundly when holding international reserves? A banking and financial vulnerabilities perspective*(Routledge Journals, Taylor & Francis Ltd, 2024) Omay, Tolga; Allegret, Jean-Pierre; Omay, Tolga; EconomicsWe use a sample of 40 developing and emerging countries over the period 1995-2015 to assess the effectiveness of international reserve holding as a crisis mitigator. We test the relevance of the reserve accumulation decreasing returns assumption by estimating the most recent version of the PSTR model. We find that increasing stocks of international reserves allows domestic authorities to mitigate the negative impacts of financial and banking vulnerabilities on GDP growth rates leading to reject the decreasing returns assumption. This evidence is robust to sensitivity checks.Article Citation Count: 1Testing the Efficiency of Emerging Markets: Evidence from Nonlinear Panel Unit Tests(Savez Ekonomista Vojvodine, 2023) Omay, Tolga; Omay, Tolga; Turguttopbaş, Pınar Neslihan; Economics; International Trade and LogisticsIn this study, we investigate market efficiency considering nonlinear-ities 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 ac-curacy in findings related to such studies.Article Citation Count: 14Is there really hysteresis in the OECD unemployment rates? New evidence using a Fourier panel unit root test(Springer, 2021) Omay, Tolga; Shahbaz, Muhammad; Stewart, Chris; EconomicsWe investigate the hysteresis hypothesis by proposing a heterogeneous panel unit root test that allows for gradually changing trends and cross-sectional dependence (CSD) among panel members using a flexible Fourier form. Inconclusive results from previous studies are potentially due to using very restrictive specifications with homogenous break structures and/or exogenously determined abrupt breaks. We seek to address these limitations by employing general specifications that are more capable of characterising the true data generation process of unemployment and by allowing for spill-over effects using a bootstrapping procedure to accommodate CSD that must be considered in a globalized world. Extensive simulations suggest that the failure to take structural breaks and CSD into account can lead to misleading conclusions about whether the unemployment rate is stationarity. We apply our test procedure to unemployment data for 23 OECD countries and find conclusive evidence against the hysteresis hypothesis for all these countries.Article Citation Count: 2The effects of energy-intensive meat production on CO2 emissions: evidence from extended environmental Kuznets framework(Springer Heidelberg, 2022) Omay, Tolga; Omay, Tolga; Bor, Özgür; Aktan, Ceyda; EconomicsThis study documents the positive relationship between meat production and CO2 emissions by utilizing the environmental Kuznets framework. Relationships between energy consumption, economic growth, meat production, and the levels of CO2 are tested using 6 different variables (CO2 emissions, GDP, energy consumption, forest area, total meat, and total livestock). Data for the study is related to the G7 countries and covers the period between 1961 and 2016. The analysis of the data is then conducted using a panel threshold model. Moreover, the extended EKC model does not only consider the income as the state variable but also examines the nonlinear structure inherited in other explanatory variables as a state variable. In this way, we have seen the nonlinear effects of other variables' evolution over time on carbon emission. The overall results indicate that the production of meat significantly increases CO2 emissions.Article Citation Count: 5Nonlinear error correction based cointegration test in panel data(Elsevier Science Sa, 2017) Omay, Tolga; Emirmahmutoglu, Furkan; Denaux, Zulal S.; EconomicsWe propose a nonlinear error correction-based cointegration test in a panel data setting and provide their small sample properties. (C) 2017 Elsevier B.V. All rights reserved.
