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
Main Affiliation
Economics
Status
Website
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
5
GENDER EQUALITY
0
Research Products
14
LIFE BELOW WATER
2
Research Products
10
REDUCED INEQUALITIES
2
Research Products
3
GOOD HEALTH AND WELL-BEING
2
Research Products
2
ZERO HUNGER
0
Research Products
9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
3
Research Products
16
PEACE, JUSTICE AND STRONG INSTITUTIONS
0
Research Products
11
SUSTAINABLE CITIES AND COMMUNITIES
1
Research Products
8
DECENT WORK AND ECONOMIC GROWTH
11
Research Products
13
CLIMATE ACTION
7
Research Products
4
QUALITY EDUCATION
0
Research Products
6
CLEAN WATER AND SANITATION
0
Research Products
1
NO POVERTY
0
Research Products
15
LIFE ON LAND
1
Research Products
17
PARTNERSHIPS FOR THE GOALS
7
Research Products
7
AFFORDABLE AND CLEAN ENERGY
3
Research Products
12
RESPONSIBLE CONSUMPTION AND PRODUCTION
1
Research Products
Documents
80
Citations
1218
h-index
20
Documents
74
Citations
1075
Scholarly Output
65
Articles
55
Views / Downloads
19/0
Supervised MSc Theses
4
Supervised PhD Theses
2
WoS Citation Count
435
Scopus Citation Count
503
WoS h-index
13
Scopus h-index
13
Patents
0
Projects
0
WoS Citations per Publication
6.69
Scopus Citations per Publication
7.74
Open Access Source
32
Supervised Theses
6
Google Analytics Visitor Traffic
| Journal | Count |
|---|---|
| Applied Economics | 5 |
| Computational Economics | 5 |
| Springer Proceedings in Business and Economics -- 4th International Conference on Banking and Fice Perspectives, ICBFP 2019 -- 2 May 2019 through 3 May 2019 -- Famagusta -- 273729 | 3 |
| Mathematics | 3 |
| Environmental Science and Pollution Research | 2 |
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60 results
Scholarly Output Search Results
Now showing 1 - 10 of 60
Article A Computationally Efficient Approximation for Fractional Differencing: First-Order Operators(Pergamon-Elsevier Science Ltd, 2026) Omay, Tolga; Baleanu, DumitruThis paper introduces the First-Order Fractional Differencing (FOFD) operator that substantially reduces the computational burden of fractional differencing for large-scale applications. While the standard Gr & uuml;nwald-Letnikov (GL) operator requires O(T2) operations for a series of length T, and recent FFT-based methods achieve O(T log T), our FOFD operator requires only O(T) operations through a simple two-point recursion. We develop an optimal weight calibration framework that ensures this computational efficiency does not compromise statistical accuracy, deriving a general formula wopt = d & sdot; (1-0.9 rho)beta(p) that adapts to the persistence structure of autoregressive processes. Empirical applications demonstrate substantial improvements: for the Chicago Fed National Financial Conditions Index with extreme persistence (rho= 0.992), optimal weight calibration reduces approximation error by 93% while preserving the autocorrelation structure of the GL operator. For a series of 10,000 observations, our method requires 20,000 operations compared to 530,000 for FFT-based methods and 50 million for standard implementations-enabling fractional differencing in real-time and high-frequency contexts previously infeasible due to computational constraints. The method's simplicity, requiring no specialized libraries and providing direct implementation through our calibration formula, makes it immediately accessible to practitioners while maintaining the long-memory properties essential for financial time series modeling.Article Citation - WoS: 11Citation - Scopus: 11Comparison of Optimization Algorithms for Selecting the Fractional Frequency in Fourier Form Unit Root Tests(Routledge Journals, Taylor & Francis Ltd, 2021) Omay, Tolga; Emirmahmutoglu, Furkan; Hussain Shahzad, Syed JawadWe compare the performance of unit root tests which include flexible Fourier trends in their testing processes. The algorithms considered are those of Broyden, Fletcher, Goldfarb and Shanno (BFGS), Berndt, Hall, Hall and Hausman (BHHH), Simplex, Genetic and grid search (GS). The simulation results indicate that derivative-free methods, such as Genetic and Simplex, have advantages over hill-climbing methods, such as BFGS and BHHH in providing accurate fractional frequencies for fractional frequency flexible Fourier form (FFFFF) unit root test. When the parameters are estimated under the alternative hypothesis of the FFFFF type of unit root test, the grid search and derivative-free methods provide unbiased and efficient estimations. We also provide the asymptotic distribution of the FFFFF unit root test. We extend the FFFFF unit root test to a panel version in order to increase the power of the test. Finally, the empirical analyses of healthcare convergence show that derivative-free methods, hill climbing and extensive grid searches can be used interchangeably. However, for big data and accurate estimation of the frequency parameters, the Simplex methodology using the bootstrap process is preferred.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: 10Citation - Scopus: 11Is There Convergence in Renewable Energy Deployment? Evidence From a New Panel Unit Root Test With Smooth and Sharp Structural Breaks(Pergamon-elsevier Science Ltd, 2023) Corakci, Aysegul; 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 econo-mies to seek out the menu of policies that ensure the worldwide success of renewable energy transformation.Article Citation - WoS: 9Citation - Scopus: 11Current 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.Doctoral Thesis Uygulanan Politikaların Süt Üretimine Etkisi: Seçilmiş Ab Ülkeleri ve Türkiye Karşılaştırması(2024) Güncer, Kemal; Omay, TolgaDünya nüfusundaki artışın, gelir artışları ile tarım ürünlerine olan talebi artırması ve tarımsal ürün talebinin bileşiminde değişikliklere yol açması beklenmektedir. Bu büyüyen gıda talebini karşılamak için tarımsal üretimde önemli artışlar gereklidir. Ancak, dünya üzerinde tarımsal üretimde kullanılabilecek arazi miktarının sınırlıdır. Bu durum, tarımda üretim artışları için birim arazide elde edilen üretim miktarının artırılması yani verimlilik artışlarının zorunlu olduğunu göstermektedir. Ayrıca tarım sektöründe devlet müdahalesi yaygın olarak uygulanmakta ve üretimdeki artışlar makroekonomik politika ve düzenlemelere bağlı kalmaktadır. Tarımsal destek politikalarının verimlilik üzerindeki etkisi desteklerin niteliğine bağlıdır. Verimlilik ölçütleri arasında kısmi faktör verimliliği (KFV) ve toplam faktör verimliliği (TFV) bulunmakta, ancak TFV literatürde daha baskın olarak kullanılmaktadır. Tarım sektöründe çalışan verilerin kalitesi dikkate alındığında geleneksel TFV yaklaşımlarının büyümenin nedenleri hakkında yeterli bilgi sağlamamakta ve büyümenin teknolojik ve kurumsal değişim, tarımsal politika ve tasarım ile ilişkilisini ele almaktadır. Bu nedenle, çalışmada, KFV ve TFV yaklaşımlarının eksikliklerini gidermek ve tarımsal büyüme üzerindeki etkileri analiz etmek amacıyla yeni bir ölçüt olarak birleştirilmiş yaklaşım geliştirilmiştir. Bu çerçevede, Türkiye'deki süt üretiminin belirleyicilerini analiz etmek ve çözümlemek amacıyla 1961-2017 dönemi üzerine odaklanılmış, aynı dönemde, hayvancılık ve süt sektörlerini yoğun şekilde destekleyen Almanya, Fransa ve Hollanda gibi üç Avrupa Birliği ülkesi ile regresyon analizini de içeren karşılaştırmalı bir çalışma yapılmıştır.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.
