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This paper compares performances of bid-ask spread measures and analyzes bond-level characteristics' effects on the bid-ask spread for Turkish sovereign bonds traded in Borsa Istanbul. We use intraday order data to establish a relative quoted bid-ask spread as a benchmark and compare bid-ask spread measures' estimation performances. Results show that low-frequency spread measures are able to proxy spread dynamics, and one of the measures, Closing Percent Quoted Spread, dominates others. Additionally, we use panel data analysis to examine bond characteristics’ effects on the bid-ask spread. Panel regression analysis points out that bond characteristics have a significant relation with bond liquidity. Bonds with shorter time to maturity or higher trading volume have narrower spreads. Also, bond type significantly affects the bid-ask spread.

In this study, the real economic activity and monetary policy in the US are examined in comparison with the foreign trade balance and exchange rates, using Qual VAR and nonlinear VAR models. We found that the foreign trade with Brazil, Canada and Mexico do not lead to a possible recession in the US. The value of the domestic currency of Brazil, Canada and Mexico against the US dollar does not contribute to a possible recession over the foreign exchange market. We also show that a contraction in the US economy and contractionary monetary policy will lead to the appreciation of the US dollar by leading to capital inflows. Although the shadow interest rate may have asymmetric effects on the foreign trade balance with Canada and USD/CAD, we find that the foreign trade balance with Mexico and USD/MXN will be affected positively/negatively by an increase/decrease in the shadow interest rate.

Objective:The aim of this study was to evaluate efficiency of time use for radiologists and operational costs of automated breast ultrasound (ABUS) versus handheld breast ultrasound (HHUS).Materials and Methods:This study was approved by the Institutional Review Board, and informed consent was waived. One hundred and fifty-three patients, aged 21–81 years, underwent both ABUS and HHUS. The time required for the ABUS scanning and radiologist interpretation and the combined scanning and interpretation time for HHUS were recorded for screening and diagnostic exams. One-Way ANOVA test was used to compare the methods, and Cohen Kappa statistics were used to achieve the agreement levels. Finally, the cost of the methods and return of interest were compared by completing a cost analysis.Results:The overall mean ± standard deviation examination time required for ABUS examination was 676.2±145.42 seconds while mean scan time performed by radiographers was 411.76±67.79 seconds, and the mean radiologist time was 234.01±81.88 seconds. The overall mean examination time required for HHUS was 452.52±171.26 seconds, and the mean scan time and radiologist time were 419.62±143.24 seconds. The reduced time translated into savings of 7.369 TL/month, and savings of 22% in operational costs was achieved with ABUS.Conclusion:The radiologist’s time was reduced with ABUS in both screening and diagnostic scenarios. Although a second-look HHUS is required for diagnostic cases, ABUS still saves radiologists time by enabling a focused approach instead of a complete evaluation of both breasts. Thus, ABUS appears to save both medical staff time and operational costs.

Bu makale, ilgili literatürün gözden geçirilmesini takiben ve çeşitlendirme, nedenleri ve beklenen etkileri içeren teorik bir arka plan ortaya koyarak, hisse senedi fiyatlarındaki oynaklık ile Borsa İstanbul'da (BIST) ve BIST Holding ve Yatırım Şirketleri endeksinde işlem gören firmaların faaliyet alanlarının çeşitlendirilmesi arasındaki ilişkiyi ortaya koymayı amaçlamaktadır. 2009-2016 yılları arasında 29 farklı şirket için yıllık konsolide finansal tablolar kullanılmaktadır. Sonuçlara göre, faaliyet alanlarının sayısı ile hisse senedi değerlerinin yıllık ortalama oynaklığı arasında negatif bir ilişki gözlemlenmiştir. Türkiye gibi gelişmekte olan piyasalarda görece yüksek piyasa riskleri göz önüne alındığında, çeşitliliğin oynaklığın azaltılmasında yararlı bir araç olmaya devam edeceği söylenebilir.

ÖZ: Bu çalışmada Borsa İstanbul’da pay senedi fiyatlarıyla işlem hacmi arasındaki ilişki 2000/01-2014/06 dönemi için incelenmiştir. Günlük işlem hacmi ile endeks verilerinin kullanıldığı araştırmada regresyon analizinin ve Granger nedensellik testinin yanı sıra Johansen Eşbütünleşme analizi ile VAR Modeli uygulanmıştır. İncelenen dönem için %5 anlamlılık düzeyinde işlem hacmi ve getiri ile getiri oynaklığı arasında eşanlı ve dinamik bir ilişki bulunmuş, fiyat değişimlerinin işlem hacimlerini etkilediği gözlemlenmiştir. Granger nedensellik testi sonuçlarına göre ise fiyat ve hacim hareketleri arasındaki ilişki tek yönlü olup, yönü fiyattan hacme doğrudur. Regresyon analiz sonuçlarını doğrulama için kurulan VAR (Vector Autoregression Model) modelinde de benzer sonuçlar gözlemlenmiş, fiyat hareketlerinin işlem hacimlerinde etkili olduğu görülmüştür. ABSTRACT: This paper investigates the stock price-volume relation in Borsa Istanbul for the period 2000/01-2014/06. Regression analysis, Granger Causality Test, Johansen Cointegration Test and VAR Model are applied by using daily index data. It is documented a dynamic and contemporaneous relation between volume and return and return volatility as well at 5 % significance level. In this study, it is found that there is a one-way causality between trading volume and return. In order to verify the results of regression analysis, the VAR Model are also analysed and the results show that the price movements affect the trading volume.