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Öğe A historical and econometric investigation of housing bubbles in OECD countries: insights from the GSADF test and machine learning(Springer, 2025) Ozgur, Onder; Yilanci, VeliThis paper investigates the existence, causes, and predictive markers of housing price bubbles in 18 OECD countries from 1870 to 2020, thus addressing a significant gap in the understanding of housing market dynamics and their implications for global financial stability. Housing bubbles have substantial impact on economic resilience and have his-torically led to severe financial crises. Employing the Generalized Supremum Augmented Dickey-Fuller (GSADF) test, this study identifies multiple bubble episodes in Australia, Denmark, Germany, Japan, Portugal, and the United States. Furthermore, by using an advanced machine learning approach, Extreme Gradient Boosting (XGBoost), this study statistically confirms the significance of interest rates, loan growth, and population growth as key predictors of housing bubbles. The findings indicate that interest rate variables are the predominant predictors, explaining over 60% of bubble dynamics in Australia and Japan, whereas credit growth and demographic factors are more influential in predicting bubbles in Germany, Denmark, and the United States. This study's originality lies in its comprehensive integration of econometric and machine learning methodologies, offer-ing more accurate, data-driven detection and prediction of housing bubbles than previ-ous research. The study's findings underscore the necessity of coordinated monetary and macroprudential policies, along with proactive demographic and credit market manage-ment, to mitigate future bubble-related risks, presenting significant implications for global policymakers and market participants.Öğe An Empirical Investigation of Explosive Price Behavior in US State-Level Electricity Markets Across Consumer Segments(Mdpi, 2025) Mert Saritas, Merve; Konat, Gokhan; Dalyanci, Levent; Yilanci, VeliThis study investigates speculative bubbles in U.S. state-level electricity markets across commercial, industrial, and residential segments. Using monthly data (2005-2025) from the U.S. Energy Information Administration and employing the Generalized Supremum Augmented Dickey-Fuller test, evidence of localized explosive price behavior was observed predominantly in Florida, Hawaii, Pennsylvania, and Oregon, among others. These bubbles, often tied to market disruptions such as fuel price volatility and post-pandemic recovery, were mainly short-lived and region-specific. The findings highlight the need for tailored, state-specific regulatory strategies to address unique market dynamics, ensuring stability amidst the ongoing energy transition.Öğe An empirical investigation of resource curse hypothesis for cobalt(Elsevier Sci Ltd, 2022) Yilanci, Veli; Turkmen, N. Ceren; Shah, Muhammad IbrahimNatural resources are considered as one of the most important factors stimulating the economic growth and development of countries. The studies concerning the relationship between the abundance of resources and economic growth, namely the resource curse, are increasing day by day and have produced conflicting results, either accepting, rejecting, or partially accepting the existence of the curse. Since the last decade, cobalt chemicals demand has radically increased because of the usage of Li-ion batteries in consumer electronics and electric vehicles. Due to the increasing importance of cobalt as a resource, this study takes an attempt to explore the resource curse hypothesis for cobalt for Australia, Canada, the Democratic Republic of Congo, Cuba, Morocco, Russia, and South Africa over the period of 2000-2018. The study employs second-generation panel data techniques in order to account for the dependency in the cross-sectional units and parameter heterogeneity. The findings of the study show that while the Democratic Republic of Congo exhibits evidence of the resource curse hypothesis for cobalt resource abundance, Canada, Cuba, and Russia reveal a positive relationship between economic growth and cobalt resource availability. For the whole panel, this study fails to find any evidence of the resource curse hypothesis in terms of Cobalt. Based on the findings, several policy implications are provided.Öğe ANALYSIS OF RELATIONSHIP BETWEEN GOVERMENT DOMESTIC DEBTS AND BASIC MACROECONOMIC INDICATORS IN TURKEY(Mehmet Akif Ersoy Univ, 2022) Gov, Abdullah; Yilanci, VeliMost of the algorithms used in the literature for the Granger (1969) causality test are based on a statistical significance test. The fact that the number of variables included in the model is sufficiently large may lead to some problems in the estimating of Granger causality test equations. Lozano et al. (2009) emphasizes that it is very important for Granger causality methods to formulate the group structure appropriately among lagged values of any time series. Bahadori and Liu (2013) stated that the Granger causality approach may not provide consistent results for a high-dimensional data set within sufficient number observations. In order to solve such problems in Granger causality tests, Granger causality approaches based on various penalized estimators are developed. The applications of Granger causality approaches based on various penalized estimators in the context of economic variables are very few in the literature. In this study, the causality relationship between goverment domestic debts and some basic macroeconomic indicators in Turkey is analyzed with Granger causality approaches based on various penalized estimators. According to the results of LASSO GN, elastic net GN and elastic net CGN tests, it was determined that there are bidirectional causal relationships between government debt, inflation, exchange rate, money supply, interest rate, industrial production index, and primary balance.Öğe Analyzing the role of income inequality and political stability in environmental degradation: Evidence from South Asia(Elsevier, 2022) Pata, Ugur Korkut; Yilanci, Veli; Hussain, Bilal; Naqvi, Syed Asif AliSouth Asian economies have experienced considerable growth over the last two decades, which has brought with it a number of problems. Despite the rapid growth, income inequality has increased in South Asia and political instability continues mainly due to territorial disputes between Pakistan and India. In addition to these factors, the increase in population and energy consumption has also contributed to the environmental problems in South Asia. Therefore, there is a need to analyze the role of income inequality and political stability in environmental degradation and thus take measures to prevent irreversible environmental consequences. In this background, this study examines the role of income inequality and political stability on environmental degradation in four South Asian countries (Pakistan, India, Sri Lanka, and Bangladesh). For this purpose, the study employs second-generation panel data approaches on a Stochastic Impacts by Regression on Population, Affluence, and Technology model (STIRPAT). Based on annual data for the period 2002-2016, the empirical results show that economic growth, income inequality, urbanization, and financial development increase the ecological footprint, while political stability and renewable energy utilization help to reduce environmental degradation. The findings of the panel causality test also suggest unidirectional causality from urbanization, renewable energy, economic growth, and income inequality to ecological footprint. According to these findings, ensuring political stability, reducing income inequality, and promoting renewable energy are essential policy instruments for sustainable and green development in four South Asian countries. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.Öğe Analyzing Türkiye's ecological footprint: the impact of air transportation, renewable energy, and R&D using a non-linear ARDL approach(Iop Publishing Ltd, 2025) Konat, Gokhan; Yilanci, Veli; Tatar, Havanur Ergun; Han, AysegulThis study investigates the complex relationship between air transportation, research and development (R&D) expenditures, renewable energy consumption, economic growth, and the ecological footprint in T & uuml;rkiye, utilizing annual data from 1990 to 2021. Employing both linear and non-linear Autoregressive Distributed Lag (ARDL) models, the study assesses the validity of the Environmental Kuznets Curve (EKC) hypothesis and explores the short- and long-run dynamics of the ecological footprint. Both the linear and non-linear ARDL models provide support for the EKC hypothesis, suggesting that economic growth may decouple from environmental degradation in the long run. Furthermore, robustness checks corroborate these findings. In the long term, air transportation exhibits asymmetric effects; while its positive components do not have a direct impact, its negative components contribute to environmental degradation in T & uuml;rkiye. Renewable energy consumption mitigates environmental pressure, whereas the impact of R&D expenditures is not statistically significant. The findings underscore the substantial influence of air transportation on T & uuml;rkiye's ecological footprint, highlighting the necessity for sustained efforts toward sustainable practices and technological advancements within the aviation sector. Moreover, the study emphasizes the importance of investments in R&D and renewable energy for achieving environmental sustainability, while also acknowledging their complex and multifaceted impacts. The paper also discusses policy recommendations and future research directions focused on achieving a balance between economic development and environmental protection in T & uuml;rkiye.Öğe Are Shocks to the Grazing Land Footprint Permanent or Transitory? Evidence from a Machine Learning-Based Unit Root Test(Mdpi, 2025) Yilanci, Veli; Ozgur, Onder; Saritas, Merve MertUnderstanding the dynamic behavior of the grazing land footprint (GLF) is critical for sustainable land management. This study examines the GLF in 92 countries to determine if the series is stationary, a statistical property indicating that shocks have transitory effects, or non-stationary, which implies that shocks have permanent, cumulative impacts (a phenomenon known as persistence). We employ a novel machine learning framework that uses an XGBoost algorithm to synthesize information from multiple conventional tests and time-series characteristics, enhancing analytical robustness. The results reveal significant cross-country heterogeneity. The GLF exhibits stationary behavior in a subset of nations, including China, India, and Norway, suggesting that their ecosystems can absorb shocks. However, for most countries, the GLF is non-stationary, indicating that ecological disruptions have lasting and cumulative impacts. These findings underscore that a one-size-fits-all policy approach is inadequate. Nations with a stationary GLF may find short-term interventions effective, whereas those with non-stationary series require profound structural reforms to mitigate long-term degradation. This highlights the critical role of advanced methodologies in shaping evidence-based environmental policy.Öğe Convergence in ecological footprint across the member states of ECOWAS: evidence from a novel panel unit root test(Springer Heidelberg, 2022) Yilanci, Veli; Ursavas, Ugur; Ursavas, NeslihanIn this paper, we investigate the convergence in ecological footprint per capita across the ECOWAS (Economic Community of West African States) countries from 1968 to 2017. For this aim, we apply a panel Fourier threshold unit root test recently proposed by Yilanci et al. (2021). This methodology considers both multiple smooth structural changes and nonlinearity, which allows us to get more reliable results. The results of the study support the evidence of nonlinearity for the series, so we test the null of divergence in a nonlinear framework. Since test statistics are statistically significant, we conclude that there is global convergence for the sample. Besides, we find that the type of convergence is absolute, which supports the view that the ecological footprint of the ECOWAS countries will equalize in the long run, and the emission allocation policies should be given priority by policymakers.Öğe Detecting and explaining bubbles in Islamic stock markets: A dual approach with LPPLS and machine learning(Borsa Istanbul Anonim Sirketi, 2026) Saritas, Merve Mert; Özgür, Önder; Yilanci, VeliThis study investigates the presence and predictability of price bubbles in Islamic stock markets, challenging the proposition that their Sharia-compliant principles provide inherent resilience against such phenomena. Employing a dual methodology, we first apply the Log-Periodic Power Law Singularity (LPPLS) model to detect crash periods in the daily Dow Jones Islamic Market indices for Canada, Japan, the United Kingdom, and the United States from 1996 to 2025. Subsequently, we utilize an eXtreme Gradient Boosting (XGBoost) algorithm to identify the key macro-financial drivers of these identified bubble episodes. The results from the LPPLS analysis confirm that these indices exhibit significant bubble dynamics. The XGBoost model incorporated imbalance-aware learners and further reveals that the probability of a bubble is systematically linked to a combination of market-based and macroeconomic variables, with the stock price index, intraday volatility, long-term interest rates, and exchange rates emerging as the most significant predictors, albeit with country-specific variations. © 2026 Borsa İstanbul Anonim Şirketi.Öğe Does financial development promote renewable energy consumption in the USA? Evidence from the Fourier-wavelet quantile causality test(Pergamon-Elsevier Science Ltd, 2022) Pata, Ugur Korkut; Yilanci, Veli; Zhang, Qianxiao; Shah, Syed Ale RazaTo achieve environmental sustainability, it is important to change the energy pattern from dirty fossil fuels to renewable-clean energy sources. For this transition, countries should use their financial re-sources effectively and efficiently. Against this background, this study aims to examine the impact of financial development on renewable energy consumption in the United States over the period 1980-2019, considering urbanization, economic structure, and economic growth as control variables. The study contributes to the existing literature by testing the effect of six sub-indicators, namely efficiency, depth, and accessibility of financial markets and institutions on renewable energy consumption. This is done using the novel Fourier quantile causality test with wavelet transforms. The empirical results show that financial development encourages renewable energy consumption at high quantiles in the medium -and long-run. Moreover, depth and access to financial markets are the two most important factors that promote renewable energy consumption. Based on the overall findings, the study suggests that the United States government should adopt policies that improve the depth and access to financial markets rather than financial institutions to support green growth. (c) 2022 Elsevier Ltd. All rights reserved.Öğe Economic and geopolitical risk factors on environmental sustainability in Türkiye: a time-varying and wavelet coherence analysis(Springer Science and Business Media B.V., 2025) Yilanci, Veli; Mike, Faruk; Ursavaş, Uğur; Kızılkaya, OktayTürkiye is one of the few countries in the world that simultaneously faces economic and geopolitical risk factors, and their impacts on environmental degradation remain highly uncertain. This study aims to investigate the dynamic effects of two major risk factors—economic policy uncertainty and geopolitical risks—on the ecological footprint in Türkiye. Using annual data from 1985 to 2021, the study employs a robust methodological approach, including Fourier cointegration and causality analyses, time-varying coefficients and causality estimations, and partial wavelet coherence. All analyses provide strong and consistent evidence that EPU improves environmental quality, whereas GPR contributes to environmental degradation in Türkiye. Specifically, long-run estimations suggest that EPU mitigates environmental degradation, while GPR exerts pressure on resource consumption. Causality analysis further reveals a unidirectional relationship from EPU to the ecological footprint. Importantly, time-varying analysis highlights that EPU has a decreasing impact on the ecological footprint, particularly after the 2008 global financial crisis, whereas GPR has an increasing impact, due to the conflicts in neighboring countries during the same period. Partial wavelet coherence analysis further confirms the dynamic nature of these associations, particularly highlighting a significant correlation between EPU, GPR, and environmental degradation. These findings underscore the importance of stable economic policies and international cooperation to mitigate geopolitical risks and reduce environmental degradation in Türkiye. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.Öğe Feverish sentiment, lockdown stringency, oil volatility, and clean energy stocks during COVID-19 pandemic(Emerald Group Publishing Ltd, 2022) Solarin, Sakiru Adebola; Gorus, Muhammed Sehid; Yilanci, VeliPurpose - This study seeks to investigate role of the coronavirus disease 2019 (COVID-19) pandemic on clean energy stocks for the United States for the period 21 January 2020-16 August 2021. Design/methodology/approach - At the empirical stage, the Fourier-augmented vector autoregression approach has been used. Findings - According to the empirical results, the response of the clean energy stocks to the feverish sentiment, lockdown stringency, oil volatility, dirty assets, and monetary policy dies out within a short period of time. In addition, the authors find that there is a unidirectional causality from the feverish sentiment index and the lockdown stringency index to the clean energy stock returns; and from the monetary policy to the clean energy stocks. At the same time, there is a bidirectional causality between the lockdown stringency index and the feverish sentiment index. The empirical findings can be helpful to both practitioners and policy-makers. Originality/value - Among the COVID-19 variables used in this study is a new feverish sentiment index, which has been constructed using principal component analysis. The importance of the feverish sentiment index is that it allows us to examine the impact of the aggregate level of fear in the economy on clean energy stocks.Öğe Forest product footprint convergence in the Amazon: A panel data analysis of ACTO countries(Elsevier, 2025) Yilanci, Veli; Kongkuah, MaxwellThis study examines the convergence of forest product footprints (FPF) among seven Amazon Cooperation Treaty Organization (ACTO) countries from 1961 to 2022. The research investigates whether FPF levels are converging or diverging across these nations, which share the Amazon rainforest. Employing a panel unit root test that accounts for smooth and sharp structural breaks, the study identifies both convergence and divergence patterns. Colombia, Ecuador, and Guyana show evidence of convergence, potentially driven by conservation policies and indigenous land management. Conversely, Brazil and Peru demonstrate divergence, likely influenced by extensive agriculture, mining, and international trade in forest products. The findings emphasize the need for coordinated regional policies within ACTO to foster sustainable forest management practices, address divergent national interests, and prioritize environmental conservation in the Amazon.Öğe Gender inequality in labor markets: a stochastic convergence study of unemployment gaps in the OECD(Emerald Group Publishing Ltd, 2025) Yilanci, Veli; Altinsoy, Abdulkadir; Unlu Bektas, Adviye DamlaPurposeThis study aims to empirically investigate the stochastic convergence of the gender unemployment gap (male minus female unemployment rates) across 30 OECD countries for the period January 2000 to December 2024. It examines the persistence of this gap, framed within the theoretical tension between unemployment hysteresis and the Law of One Rate of Unemployment (LOOUR).Design/methodology/approachThe study employs the robust Bahmani-Oskooee, Chang, and Wu (BCW) panel unit root test, which innovatively accounts for both sharp structural breaks and smooth, nonlinear dynamics through Fourier functions, while being robust to cross-sectional dependence.FindingsThe findings reveal substantial evidence of stochastic convergence for a majority of the panel (25 out of 30 countries), meaning their individual gender unemployment gaps tend to revert towards the OECD average gender unemployment gap. This suggests that for these nations, shocks causing their gender unemployment gap to deviate from the OECD average are largely transitory.Originality/valueThis research offers a novel methodological perspective by directly examining the dynamic properties of the gender unemployment gap itself as a time series using advanced panel unit root tests. It contributes by empirically testing the LOOUR versus hysteresis debate specifically for gender-differentiated unemployment and provides evidence supporting tailored policy interventions to address both transitory and structural components of these disparities in developed labor markets.Öğe Impact of Monetary Aggregates on Consumer Behavior: A Study on the Policy Response of the Federal Reserve against COVID-19(Kasersart Univ, Fac Economics, 2022) Kilci, Esra N.; Yilanci, VeliConsumers have tended to sharply decrease their spending during the COVID-19 pandemic due to pessimistic expectations related to the economic outlook, concerns about their jobs, and a decline in incomes. The Federal Reserve has taken several measures in response to the pandemic, resulting in increases in the money supply and asset sizes. This study aims to analyze the impact of monetary aggregates on consumer behavior before and after the pandemic by employing the bootstrap autoregressive distributed lag (ARDL) cointegration test with an exogenous structural break. The US money supply (M3) and total assets are used as dependent variables and consumer expenditure, consumer credit, and consumer sentiment are the independent variables. The data employed cover the period from January 2003 to August 2020. The results show cointegration relationships among consumer expenditure, the US money supply (M3), and total assets. The effect of the FED???s policy response on consumer behavior has strengthened after the pandemic.Öğe Is the environmental Kuznets curve related to the fishing footprint? Evidence from China(Elsevier, 2022) Yilanci, Veli; Cutcu, Ibrahim; Cayir, BilalThis study tests the validity of the environmental Kuznets curve (EKC) hypothesis by using the fishing grounds footprint (FGF) as the environmental degradation indicator in China from 1961 to 2017. The study also uses China's total fisheries production as a control variable. Since the results of the analysis indicate a long-run relationship between the variables, we estimate the long- and short-run coefficients that present evidence for the validity of the EKC in the long-run. We find that total fisheries production has a detrimental effect on the environment. The findings of the study have important policy implications for decision-makers: Implementing a common fishing policy at the regional and global levels to stabilize the FGF and using new technologies that are harmless to the environment at every stage of fishery production processes may be beneficial for the environment.Öğe Nuclear energy consumption and CO2 emissions in India: Evidence from Fourier ARDL bounds test approach(Korean Nuclear Soc, 2022) Ozgur, Onder; Yilanci, Veli; Kongkuah, MaxwellThis study uses data from 1970 to 2016 to analyze the effect of nuclear energy use on CO2 emissions and attempts to validate the EKC hypothesis using the Fourier Autoregressive Distributive Lag model in India for the first time. Because of India's rapidly rising population, the environment is being severely strained. However, with 22 operational nuclear reactors, India boasts tremendous nuclear energy potential to cut down on CO2 emissions. The EKC is validated in India as the significant coefficients of GDP and GDP.2 The short-run estimates also suggest that most environmental externalities are corrected within a year. Given the findings, some policy recommendations abound. The negative statistically significant coefficient of nuclear energy consumption is an indication that nuclear power expansion is essential to achieving clean and sustainable growth as a policy goal. Also, policymakers should enact new environmental laws that support the expansion and responsible use of nuclear energy as it is cleaner than fossil fuels and reduces the cost and over-dependence on oil, which ultimately leads to higher economic growth in the long run. Future research should consider studying the nonlinearities in the nuclear energy-CO2 emissions nexus as the current study is examined in the linear sense. (c) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Öğe Stochastic convergence of nitrogen oxides by fuel for OECD countries covering 1820-2019(Sage Publications Ltd, 2023) Solarin, Sakiru Adebola; Yilanci, Veli; Gorus, Muhammed SehidAddressing the challenges posed by pollutants is necessary to achieve the Sustainable Development Goals (SDGs) target 12 or achieve sustainable production and consumption patterns. Convergence assessment of air pollution provides information which can be beneficial to how to handle that air pollution across different countries. Nitrogen oxides (NOx) are one of the most popular air pollutants. However, the current empirical literature on environmental economics largely ignores the convergence of per capita NOx. For this reason, this study investigates the stochastic convergence of aggregate and fuel-specific per capita NOx emissions in 20 OECD countries. This paper employs a recently introduced panel stationarity test that considers both smooth and sharp structural changes in the data generation process. The panel results show that the convergence hypothesis is rejected only for NOx from light-oil consumption. However, country-specific results reveal substantial evidence for divergence in the sample countries when NOx emissions per capita generated through diesel consumption, light-oil consumption, and natural gas consumption are considered. Besides, we find that most of the series have convergent behaviour for aggregate NOx, NOx from biomass consumption, NOx from hard-coal consumption, NOx from heavy-oil consumption, and NOx from the process. The policy implications of the empirical results for proper environmental management are elucidated in the paper. Actions taken based on the convergence findings will likely lead to a decrease in NOx emissions per capita as the countries will converge towards a lower level of NOx emissions per capita, in line with SDG's target 12.Öğe Testing Real Interest Rate Parity for EU5 Countries: 200 Years of Data, Non-normality, Non-linearity and Breaks(Prague Univ Economics And Business, 2025) Yilanci, Veli; Ozgur, OnderPurpose: This paper aims to examine the real interest rate parity (RIP) theory for EU5 countries (France, Germany, Italy, Spain and the UK) versus the USA. Design/methodology/approach: Utilizing RALS-FADF and RALS-FKSS unit root tests, this study addresses non-normality, non-linearity and structural breaks in real interest rate differentials. Findings: The results confirm the RIP theory, indicating mean reversion of real interest rate differentials and highlighting impact of financial integration on monetary policy independence and arbitrage opportunities. The study notes that central banks' ability to influence domestic economies through interest rates is limited due to global financial interconnectedness. Originality/value: The paper offers a new test and bases its empirical setup on whether interest rate differentials are non-normally distributed. The test also considers real interest rate non-linearity and the non-normality in the analysis.Öğe Testing the Persistence of Shocks on Ecological Footprint and Sub-accounts: Evidence from the Big Ten Emerging Markets(Springer Int Publ Ag, 2022) Yilanci, Veli; Pata, Ugur Korkut; Cutcu, IbrahimThis study aims to analyze whether the effect of shocks on the ecological footprint and its sub-accounts in the Big Ten emerging economies is transitory or not. To this end, we employ the Fourier augmented Dickey-Fuller unit root test with a fractional frequency (FADF) and the recently developed fractional unit root test with a Fourier function (FUR) on annual data from 1961 to 2017. The results of the FADF unit root test suggest the validity of stationarity for about 30% of the series, while the FUR test indicates evidence of stationarity for almost all footprint series. These results imply that policy shocks to ecological footprints are temporary and policies to reduce environmental pollution in the Big Ten countries do not have the expected impact. Since shocks have temporary effects on ecological footprints, the Big Ten countries should not cause irreversible environmental degradation. The Big Ten governments need to implement permanent structural reforms to counteract the growth of the ecological footprint. Article Highlights The persistence of the ecological footprint and its six subaccounts in the Big Ten emerging markets is investigated. Novel Fourier-based and fractional frequency unit root tests are performed. Almost all series are stationary. Policy shocks will have temporary effects on the ecological footprint.
