32 results
Search Results
Now showing 1 - 10 of 32
Article Citation - WoS: 5Doğrusal Olmayan Birim Kök Testleri Kullanılarak 21 Oecd Ülkesinde Sağlık Harcamaları Yakınsamasının Test Edilmesi(Duzce Univ, Fac Medicine, 2022) Çelik, Eşref Uğur; Omay, Tolga; Tuzlukaya, ŞuleAmaç: Bu çalışma, 1975 ve 2019 yılları için 21 OECD ülkesinde sağlık harcamalarının stokastik zaman serisi davranışını bir dizi güncel birim kök testi kullanarak analiz etmeyi amaçlamaktadır. Gereç ve Yöntem: Bu çalışmada, 21 OECD ülkesinin sağlık harcaması verilerinin bu ülkelerin sağlık harcamaları arasında bir yakınsama olup olmadığını ampirik olarak test etmek için doğrusal ADF birim kök testi ve sekiz ilgili doğrusal olmayan birim kök testi kullanılmıştır. Bulgular: Ampirik bulgular, 21 OECD ülkesinin 20'sinde sağlık harcamalarının durağanlığını desteklemektedir. Sonuç: OECD ülkelerinin çoğunda sağlık yakınsama hipotezi doğrulanmış olup, sağlık harcamaları şoklarının ülke düzeyinde sağlık harcamaları üzerinde yalnızca geçici etkileri olduğunu göstermektedir. Bu ampirik çalışma çok önemli politika sonuçları sunmaktadır. Politika otoritelerinin alacağı politika tedbirlerinin sağlık harcamaları verisindeki olası doğrusal olmayanlığı göz ardı edilerek yapılamayacağı çalışmanın ampirik kısmında teyit edilmiştir. Sonuç kısmında sıralanan politika önerilerine alt rejim dönemlerinde daha fazla yatırım yapılması ve yüksek rejim dönemlerde ise var olanın sürdürülmesinin sağlık harcamaları yakınsaması için yeter koşul sağladığı belirlenmiştir. Bunun yanı sıra Japonya ve Güney Kore gibi ülkelerde rejimden bağımsız yapısal değişimlerin sağlık harcamaları yakınsamasında da değişim yarattığı belirlenmiştir. Bu tarz ülkelerde yapısal değişimler gözetilerek yatırımların yapılması önem arz etmektedir.Article Citation - WoS: 6Citation - Scopus: 4Is real per capita state personal income stationary? New nonlinear, asymmetric panel-data evidence(Wiley, 2020) Emirmahmutoglu, Furkan; Gupta, Rangan; Miller, Stephen M.; Omay, TolgaThis paper re-examines the stochastic properties of U.S. state real per capita personal income, using new panel unit-root procedures. The new developments incorporate non-linearity, asymmetry, and cross-sectional correlation within panel-data estimation. Including nonlinearity and asymmetry finds that 43 states exhibit stationary real per capita personal income whereas including only nonlinearity produces 42 states that exhibit stationarity. Stated differently, we find that two states exhibit nonstationary real per capita personal income when considering nonlinearity, asymmetry, and cross-sectional dependence.Article Citation - WoS: 11Testing the Hysteresis Effect in the Us State-Level Unemployment Series(Routledge Journals, Taylor & Francis Ltd, 2020) Omay, Tolga; Ozcan, Burcu; Shahbaz, MuhammedThis paper re-examines the stochastic time series behaviour of the monthly unemployment rate in 50 states of the United States (US) for the period 1976-2017 using a number of state-of-the-art unit root tests. The new developments incorporate structural break, nonlinearity, asymmetry, and cross-sectional correlation within panel-data estimation including the use of a sequential panel selection method. While not previously considered, sequential panel selection enabled us to determine and separate the stationary and nonstationary series in the sample. The empirical findings are in support of the stationarity of unemployment rate in 47 states. The findings confirm a natural rate hypothesis for the labour markets in the most US states, indicating that labour market shocks have solely temporary effects on state-level unemployment. This empirical study provides significant state-specific policy implications.Article Hisse Senedi Getirileri, Bitcoin Getirileri ve Riskten Kaçınma Arasındaki İlişki: Çok Değişkenli Bir Garch Modelinden Kanıtlar(Sosyoekonomi Soc, 2021) Sivrikaya, Ayşen; İren, Perihan; Omay, TolgaBu çalışma, çok değişkenli bir GARCH modeli kullanarak ABD Dow Jones Borsasında işlem gören hisse senedi getirileri, Bitcoin getirileri ve bunların belirsizlikleri arasındaki ilişkileri araştırmaktadır. Özellikle, yüksek ve düşük olmak üzere farklı risk iştahının ve getirilerde belirsizliğin yüksek olduğu dönemlerde Bitcoin ve ABD hisse senedi getirilerinin verdiği tepkileri karşılaştırmaktadır. Sonuçlar, Bitcoin getirisinin riskten kaçınılan veya yüksek belirsizliğin olduğu dönemlerde hisse senedi gibi tepki verdiğini, ancak iki getiri arasındaki ilişkinin sürdürülebilir olmadığını göstermektedir. Öte yandan, ABD borsa yatırımcıları tüm örneklem dönemi boyunca riskten kaçınma davranışını gösterirken, Bitcoin yatırımcıları aynı davranışı göstermemektedir.Article Citation - WoS: 30Citation - Scopus: 34Fractional Unit-Root Tests Allowing for a Fractional Frequency Flexible Fourier Form Trend: Predictability of Covid-19(Springer, 2021) Omay, Tolga; Baleanu, DumitruIn this study we propose a fractional frequency flexible Fourier form fractionally integrated ADF unit-root test, which combines the fractional integration and nonlinear trend as a form of the Fourier function. We provide the asymptotics of the newly proposed test and investigate its small-sample properties. Moreover, we show the best estimators for both fractional frequency and fractional difference operator for our newly proposed test. Finally, an empirical study demonstrates that not considering the structural break and fractional integration simultaneously in the testing process may lead to misleading results about the stochastic behavior of the Covid-19 pandemic.Article Citation - WoS: 8Citation - Scopus: 10Current Account and Credit Growth: the Role of Household Credit and Financial Depth(Elsevier Science inc, 2020) Ekinci, Mehmet Fatih; Ekinci, Mehmet Fatih; Omay, Tolga; Omay, Tolga; Ekinci, Mehmet Fatih; Omay, Tolga; Economics; EconomicsUnderstanding the impact of financial variables on the current account balance is one of the priorities of academic literature and policymakers. Evidence from a broad panel of advanced and emerging countries shows that an increase in credit growth is associated with a significant deterioration in the current account balance. When we examine the roles of the components of credit, we find that an increase in household credit causes a significant decline in the current account balance, whereas an increase in business loans has no significant effect. Therefore, our findings indicate that the significant negative impact of credit growth on the current account balance is driven by household credit. Furthermore, we show that total and household credit growth rates have a stronger negative effect on the current account balance for lower levels of financial depth. Our results suggest that targeted policy measures that curb household credit growth might be more effective to reduce external imbalances particularly at the early stages of financial deepening.Article Citation - WoS: 2Citation - Scopus: 2Phase and Wave Dependent Analysis of Health Expenditure Efficiency: a Sample of Oecd Evidence(Frontiers Media Sa, 2023) Boduroglu, Elif; Atici, Kazim Baris; Omay, TolgaIntroductionHealth 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. MethodIn 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. ConclusionThe 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. DiscussionThe 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 Representation of Omitted Variable Bias With the Total Derivative Method(Universal Wiser Publisher, 2024) Omay, Tolga; Elitas, ZeynepThis study aims to provide an understanding of the concept of omitted variable bias through the total derivative method. This novel approach that is often overlooked could bring a new perspective to statisticians, econometricians, or researchers in neighboring disciplines such as social sciences, management, or economics. In order to complement this mathematical method, the study also employs graphical representations. By doing so, we provide a detailed walkthrough of the total derivative method, its visual depiction, and its application to the omitted variable bias. We believe that this approach can enhance the understanding of regression analysis and foster a deeper connection between mathematics and econometrics. Overall, this study can contribute to the development of new theoretical foundations using the total differential method in this context.Article Citation - WoS: 8Citation - Scopus: 10Convergence of Economic Growth and Health Expenditures in Oecd Countries: Evidence From Non-Linear Unit Root Tests(Frontiers Media Sa, 2023) Celik, Esref Ugur; Omay, Tolga; Tengilimoglu, DilaverIntroductionThe 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. MethodsIn 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. ResultsThe 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. DiscussionPolicymakers 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 Citation - WoS: 2Citation - Scopus: 1Comparison of the Performance of Structural Break Tests in Stationary and Nonstationary Series: a New Bootstrap Algorithm(Springer, 2024) Camalan, Ozge; Hasdemir, Esra; Omay, Tolga; Kucuker, Mustafa CanStructural breaks are considered as permanent changes in the series mainly because of shocks, policy changes, and global crises. Hence, making estimations by ignoring the presence of structural breaks may cause the biased parameter value. In this context, it is vital to identify the presence of the structural breaks and the break dates in the series to prevent misleading results. Accordingly, the first aim of this study is to compare the performance of unit root with structural break tests allowing a single break and multiple structural breaks. For this purpose, firstly, a Monte Carlo simulation study has been conducted through using a generated homoscedastic and stationary series in different sample sizes to evaluate the performances of these tests. As a result of the simulation study, Zivot and Andrews (J Bus Econ Stat 20(1):25-44, 1992) are the best-performing tests in capturing a single break. The most powerful tests for the multiple break setting are those developed by Kapetanios (J Time Ser Anal 26(1):123-133, 2005) and Perron (Palgrave Handb Econom 1:278-352, 2006). A new Bootstrap algorithm has been proposed along with the study's primary aim. This newly proposed Bootstrap algorithm calculates the optimal number of statistically significant structural breaks under more general assumptions. Therefore, it guarantees finding an accurate number of optimal breaks in real-world data. In the empirical part, structural breaks in the real interest rate data of the US and Australia resulting from policy changes have been examined. The results concluded that the bootstrap sequential break test is the best-performing approach due to the general assumption made to cover real-world data.
