Omay, Tolga

Profile URL
https://hdl.handle.net/20.500.14411/7237
Name Variants
T.,Omay 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
23978235900
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
GDI-4259-2022
No research topics data found.

Sustainable Development Goals

NO POVERTY1
NO POVERTY
0
Research Products
ZERO HUNGER2
ZERO HUNGER
0
Research Products
GOOD HEALTH AND WELL-BEING3
GOOD HEALTH AND WELL-BEING
2
Research Products
QUALITY EDUCATION4
QUALITY EDUCATION
0
Research Products
GENDER EQUALITY5
GENDER EQUALITY
0
Research Products
CLEAN WATER AND SANITATION6
CLEAN WATER AND SANITATION
0
Research Products
AFFORDABLE AND CLEAN ENERGY7
AFFORDABLE AND CLEAN ENERGY
3
Research Products
DECENT WORK AND ECONOMIC GROWTH8
DECENT WORK AND ECONOMIC GROWTH
11
Research Products
INDUSTRY, INNOVATION AND INFRASTRUCTURE9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
3
Research Products
REDUCED INEQUALITIES10
REDUCED INEQUALITIES
2
Research Products
SUSTAINABLE CITIES AND COMMUNITIES11
SUSTAINABLE CITIES AND COMMUNITIES
1
Research Products
RESPONSIBLE CONSUMPTION AND PRODUCTION12
RESPONSIBLE CONSUMPTION AND PRODUCTION
1
Research Products
CLIMATE ACTION13
CLIMATE ACTION
7
Research Products
LIFE BELOW WATER14
LIFE BELOW WATER
2
Research Products
LIFE ON LAND15
LIFE ON LAND
1
Research Products
PEACE, JUSTICE AND STRONG INSTITUTIONS16
PEACE, JUSTICE AND STRONG INSTITUTIONS
0
Research Products
PARTNERSHIPS FOR THE GOALS17
PARTNERSHIPS FOR THE GOALS
7
Research Products
Documents

82

Citations

1250

h-index

20

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Documents

74

Citations

1101

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No records found in other affiliations.
Scholarly Output

68

Articles

58

Views / Downloads

82/201

Supervised MSc Theses

4

Supervised PhD Theses

2

WoS Citation Count

456

Scopus Citation Count

528

Patents

0

Projects

0

WoS Citations per Publication

6.71

Scopus Citations per Publication

7.76

Open Access Source

34

Supervised Theses

6

JournalCount
Computational Economics6
Applied Economics5
Mathematics3
Springer Proceedings in Business and Economics -- 4th International Conference on Banking and Fice Perspectives, ICBFP 2019 -- 2 May 2019 through 3 May 2019 -- Famagusta -- 2737293
Environmental Modeling & Assessment2
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Scholarly Output Search Results

Now showing 1 - 10 of 68
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Controlling Heterogeneous Structure of Smooth Breaks in Panel Unit Root and Cointegration Testing
    (Springer, 2021-11-01) Omay, Tolga; Iren, Perihan
    This 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
    A Computationally Efficient Approximation for Fractional Differencing: First-Order Operators
    (Pergamon-Elsevier Science Ltd, 2026-04) Omay, Tolga; Baleanu, Dumitru
    This 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: 11
    Citation - Scopus: 11
    Comparison of Optimization Algorithms for Selecting the Fractional Frequency in Fourier Form Unit Root Tests
    (Routledge Journals, Taylor & Francis Ltd, 2020-10-20) Omay, Tolga; Emirmahmutoglu, Furkan; Hussain Shahzad, Syed Jawad
    We 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: 9
    Citation - Scopus: 11
    Current Account and Credit Growth: the Role of Household Credit and Financial Depth
    (Elsevier Science inc, 2020-11) Ekinci, Mehmet Fatih; Ekinci, Mehmet Fatih; Omay, Tolga; Omay, Tolga; Ekinci, Mehmet Fatih; Omay, Tolga; Economics; Economics
    Understanding 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, Tolga
    Dünya 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
    Hisse Senedi Getirileri, Bitcoin Getirileri ve Riskten Kaçınma Arasındaki İlişki: Çok Değişkenli Bir Garch Modelinden Kanıtlar
    (Sosyoekonomi Soc, 2021-01-25) Sivrikaya, Ayşen; İren, Perihan; Omay, Tolga
    Bu 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: 31
    Citation - Scopus: 35
    Fractional Unit-Root Tests Allowing for a Fractional Frequency Flexible Fourier Form Trend: Predictability of Covid-19
    (Springer, 2021-03-15) Omay, Tolga; Baleanu, Dumitru
    In 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: 1
    Makroekonomik ve Sosyo-Politik Endeks Nitelikli Çalışan başına Reel GSYH’yi Nasıl Etkiler? Türk Cumhuriyetleri’nden Kanıtlar
    (Ahmet Yesevi Univ, 2023-04-27) Kucuker, Mustafa Can; Omay, Tolga; Celik, Esref Ugur; Erdal, Fehmi Buğra
    Bu çalışmada, nitelikli çalışan başına reel GSYH düzeyini etkileyen sosyoe- konomik faktörler üzerinde durulmuştur. Bu amaçla Türk Cumhuriyetleri için makroekonomik ve sosyo-politik performans endeksleri oluşturulmuştur. Yeni oluşturulan bu endeksler kullanılarak, nitelikli çalışan başına düşen reel GSYH düzeyinin belirleyicileri literatürde ilk kez analiz edilmektedir. Ampi- rik sonuçlar, belirli eşik düzeylerinin nitelikli çalışan başına reel GSYH düze- yini önemli ölçüde etkilediğini göstermektedir. Sonuç olarak, çalışmada yer verilen ülkelerin politika yapıcıları, ülkelerinin refahı açısından iyi organize edilmiş politikalar yürütmek için makroekonomik ve sosyo-politik perfor- mans endekslerin eşik değerlerini ciddi şekilde göz önünde bulundurmalıdır.
  • Article
    Citation - WoS: 48
    Citation - Scopus: 48
    Global Risk Aversion and Emerging Market Return Comovements
    (Elsevier Science Sa, 2018-12) Demirer, Riza; Omay, Tolga; Yuksel, Asli; Yuksel, Aydin
    Utilizing the recently developed measure of global risk aversion by Xu (2017), we show that global risk aversion is a significant determinant of international equity correlations, consistently across all emerging markets examined. The positive effect of risk aversion on emerging market comovements is particularly strong for South Africa and Turkey and is consistent with contagion effects. The results underscore the importance of non-cash flow shocks in models of contagion and portfolio risk. (C) 2018 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 6
    Oil and Stock Prices: New Evidence From a Time Varying Homogenous Panel Smooth Transitionvecmfor Seven Developing Countries
    (Wiley, 2020-10-05) Ceylan, Resat; Ivrendi, Mehmet; Shahbaz, Muhammed; Omay, Tolga
    This paper investigates the relationship between international oil price and stock prices applying the time varying causality testing over the period of 2000(M1)-2017(M3). The panel unit root and panel cointegration tests considering cross-section dependence are also employed. A time varying panel smooth transition vector error correction (TV-PSTRVEC) model is a developed and estimated for testing the presence of non-linear short-run and long-run causality, and cointegrating relationship between stock and oil prices. The empirical findings indicate that short and long-run causalities between oil price and stock prices are time-dependent. Moreover, oil price cause stock prices in the long-run. In the short-run, neutral effect exists between oil price and stock prices. These two findings are evidence of a strong exogeneity of oil price in time-dependent regimes which is also supporting the recent arguments and empirical findings.