Mustafa Yilmaz

The relationship between two important macroeconomic indicators, inflation and unemployment, has been extensively studied by economists. The inverse relationship between these two variables is often referred to as the Phillips curve. However, studies have shown that the inverse relationship between these two variables does not always hold. To this end, the validity of the Phillips curve is investigated using monthly inflation and unemployment data for the Türkiye's economy from January 2005 to August 2025. The relationship between these data is examined using current tests such as the Fourier-based Quantile Toda-Yamamoto causality test and wavelet transform consistency. The study's results generally show that the Phillips curve is invalid. However, evidence supporting the validity of the Phillips curve in the Türkiye's economy has been found for certain periods. These findings are limited to the relationship between the youth unemployment rate and the consumer price index.

Unregistered employment, which is a worldwide economic problem, is also a difficult economic problem for the Türkiye’s economy. When academic studies on informal employment are examined, it is seen that these studies are generally aimed at defining and measuring informal employment in economies or explaining the relationship between informal employment and other macroeconomic data. On the other hand, this study examines whether agriculture-adjusted informal employment is persistent for the Türkiye’s economy by using data from the Turkish Statistical Institute for the period 2010/01-2021/12. To analyze the persistence of informal employment, the Fourier ADF test is used in addition to classical unit root tests. The findings reveal that agriculture-adjusted informal employment in Türkiye is heritable. The study reveals that there have been periodic improvements in the fight against informal employment in Türkiye, but this success is not sustainable without permanent legal regulations and stable policy implementation. As a policy recommendation, the study suggests that structural reforms should be made for Türkiye to achieve lasting success in the field of informal employment and that these reforms should be determined.

The approach of evaluating the final scores of multi-criteria decision-making (MCDM) methods according to the strength of association with real-life rankings is interesting for comparing MCDM methods. This approach has recently been applied mostly to financial data. In these studies, where it is emphasized that some methods show more stable success, it would be useful to see the results that will emerge by testing the approach on different data structures more comprehensively. Moreover, not only the final MCDM results but also the performance of normalization techniques and data types (fuzzy or crisp), which are components of MCDM, can be compared using the same approach. These components also have the potential to affect MCDM results directly. In this direction, in our study, the economic performances of G-20 (Group of 20) countries, which have different data structures, were calculated over ten different periodic decision matrices. Ten different crisp-based MCDM methods (COPRAS, CODAS, MOORA, TOPSIS, MABAC, VIKOR (S, R, Q), FUCA, and ELECTRE III) with different capabilities were used to better visualize the big picture. The relationships between two different real-life reference anchors and MCDM methods were used as a basis for comparison. The CODAS method develops a high correlation with both anchors in most periods. The most appropriate normalization technique for CODAS was identified using these two anchors. Interestingly, the maximum normalization technique was the most successful among the alternatives (max, min–max, vector, sum, and alternative ranking-based). Moreover, we compared the two main data types by comparing the correlation results of crisp-based and fuzzy-based CODAS. The results were very consistent, and the “Maximum normalization-based fuzzy integrated CODAS procedure” was proposed to decision-makers to measure the economic performance of the countries.

Kayıt dışı ekonomi resmi kayıtlarda, yasal belgelerde bulunmayan, yasal düzenlemeler ile kontrol edilemeyen ve dolayısıyla ulusal hesaplamalarda yer almayan ekonomik ve mali işlemlerdir. Bu çalışma temelde 3 bölümden oluşmuştur. Birinci bölümün amacı kayıt dışı ekonomi kavramını açıklığa kavuşturmaktır. Bu bağlamda ilgili bölümde kavramsal bir çerçeve sunulmaya çalışılmıştır. İkinci bölümde ise kayıt dışı ekonominin temel özellikleri irdelenmiş ona yol açan sebepler ele alınmıştır. Ek olarak kayıt dışı ekonominin yarattığı sonuçlar da incelenmiştir. 3. Bölümde ise kayıt dışı ekonominin Türkiye ekonomisindeki temel makro ekonomik göstergelerle bağlantısı ele alınmıştır. Çalışma, Türkiye’de kayıt dışı ekonominin büyüklüğü üzerine yapılan tartışmaları bir arada ele almıştır. Böylece literatürde yer alan çalışmaların sonuçlarını değerlendirme olanağı da ortaya çıkmıştır. Üçüncü bölümde ek olarak kayıt dışı ekonominin yarattığı sorunlar ve buna karşı uygulanacak politika önerilerinde de bulunulmuştur. Kayıt dışı ekonomiye ilişkin ölçüm güçlükleri, konunun önemi oranında yayın yapılmaması sonucunu doğurmuştur. Literatürde konunun önemine dikkat çeken yeterli çalışma bulunmamaktadır. Bu bağlamda bu çalışma ile literatüre katkı sağlanması amaçlanmıştır. Son olarak politika yapıcılara kayıt dışı ekonominin yol açtığı sorunları hafifletmeye yarayacak politika önerilerinde bulunulmuştur.

Unemployment is among the main economic problems not only for developed countries but also for underdeveloped countries. The European Union, which was mostly composed of developed Western European countries until 2004, has grown with the participation of Eastern European countries in the following years. In its current form, the European Union consists of countries with different levels of development. The European Union should undoubtedly consider this structure of the union in the economic policies it develops. The existence of unemployment hysteresis, which shows the situation in which unemployment, which increased after an economic shock, does not return to its former levels, is important for policymakers of the union countries, especially in terms of methods of combating unemployment. This study aims to examine unemployment hysteresis for the EU-15 and EU-28 over the average values in the 2001Q1-2019Q4 period. In addition to the traditional unit root tests of Augmented Dickey Fuller (ADF) and Phillips Perron (PP), the Fractional Frequency Fourier ADF Unit Root Test developed by Bozoklu et al. (2020) has been used as the methodology. The data are obtained from Eurostat, the official website of the European Union where statistics are published. As a result of the study, evidence is found that the hysteresis hypothesis is valid in EU-15 and EU-28 according to all three analyzes used. In the study, the use of the Fractional Frequency Fourier ADF Unit Root Test, which is the most up-to-date test, contributes to the literature.

One of the most basic assumptions of economics is that human beings are rational. The field of economics refers to this hypothetical human type as “Homo Economicus”. Thus, the behavioral and psychological characteristics of the human factor in mainstream economics have not found much study area. However, thanks to the fields of behavioral economics, experimental economics, and neuroeconomics that have developed in recent years, it has begun to be investigated in economics literature with the help of other disciplines, especially psychology, too. Along with these studies, the structure of the brain has met with economics, especially neuroeconomics, in studies conducted after the 2000s. However, most of these studies have primarily focused on microeconomic analysis. Macroeconomic issues related to the brain have been addressed only to a limited extent in the economics literature.The aim of the study is to contribute to the literature by establishing a relationship between the brain and economic growth. In the study, the relationship between the human brain and economic growth is discussed on the basis of the concept of entrepreneurship. While evaluating the concept of entrepreneurship, studies on the right brain, which is the creative and innovative side of the brain, have been examined. As a result of the study, it was concluded that individuals who is right-brain dominant and use this lobe effectively will be successful entrepreneurs and thus contribute to economic growth. In addition, recommendations for the development of the right brain and the identification and support of potential right-brain dominant entrepreneurs are presented as a result of the review.

Agriculture, which has historically been the main employment generating sector, is still very important in newly industrializing countries such as Turkey. Theoretically, it is thought that its share in GNP will decrease over time, but the depth of the decrease will depend on the economic impact of agriculture. One way to measure this effect is to adapt the Phillips curve for the agricultural sector. Therefore, the aim of this study is to analyse the validity of the Phillips curve in the Turkish agricultural sector. The study is conducted by the Augmented Dickey Fuller, Phillips Perron and Zivot-Anders Unit Root Tests as well as Nonlinear Autoregressive Distributed Lag and Autoregressive Distributed Lag tests via TURKSTAT 2014Q1-2020Q3 dataset. Reviewing these test, we find that the cointegration coefficient calculated by the NARDL model is negative, yet statistically significant. Accordingly, the short-term imbalances are eliminated in the long-run and the system converges to the long-run equilibrium values. Nonetheless, since the coefficient is greater than one, it is a sign of significant fluctuations in the convergence of the system to the long-term equilibrium. Additionally, the long-run negative cointegrated relationship of unemployment and inflation indicates that the Phillips Curve is valid in Turkish agricultural sector.

Okun's Law asserts an inverse relationship between unemployment and economic growth in the economy. The study examines the relationship between the growth rate and unemployment rate for Turkey's agricultural sector from 2014Q1 - 2021Q3. The stationarity test is carried out with the Generalized Dickey-Fuller Unit Root Test. Then, the relationship between growth and unemployment rates in the agricultural sector is analysed with the ARDL bounds test. According to the study results, the growth rate of the agricultural sector and the unemployment rate in the agricultural sector are cointegrated in the long run, and the relationship between them is statistically significant and positive. The result reached in the study; Okun's Law is valid in the agricultural sector of the Turkish economy.

Tax revenues are one of the main factors necessary for the continuation of the economic activities of the countries. Tax revenues are of vital importance for countries. Collection of all accrued taxes increases public revenues. However, not all accrued taxes can be collected. In the study, the relationship between the accrual/collection rate of taxes and economic growth was investigated using annual data for the period 1970-2020. ARDL Boundary Test is used to investigate the relationship between the variables. According to the results of the study, there is a significant long-term relationship between tax collection rates and economic growth. In addition, according to the results of the long-term coefficient equation, a positive and significant result was determined between the accrual/collection rate of taxes and economic growth.

Bütçe kanunu gereğince her yıl bir sonraki yıl için vergi gelirleri tahmin edilmektedir. Ancak ekonomik konjonktür sebebi ile tahmin edilen vergi gelirleri ile tahsil edilen vergi gelirleri arasında farklılıklar oluşmaktadır. Ekonomik konjonktürün seyrine göre vergi tahsilatı planlanandan fazla veya düşük olarak gerçekleşebilmektedir. Bu durum çalışmada vergi tahmin sapması olarak nitelendirilmektedir. Çalışmada vergi tahmin sapması ile ekonomik büyüme arasındaki ilişki araştırılmıştır. Çalışmada veriler öncelikle Augmented Dickey Fuller birim kök testi ile durağanlık sınamasına tabi tutulmuştur. Ardından değişkenler arasındaki ilişki Johansen Eşbütünleşme Testi ve Etki-Tepki analizi ile araştırılmıştır. Johansen Eşbütünleşme testinin sonucuna göre her iki değişkende birbiri ile eşbütünleşiktir. Etki tepki analizinin sonuçlarına göre ise değişkenlerde meydana gelen şoklar 3 dönem boyunca diğer değişken üzerinde etki oluşturmaktadır.