In this study, different from previous studies, the explanatory power of Student-t distribution is compared to normal distribution by employing both standard GARCH and EGARCH models to dollar/ lira (USD/TRY) exchange rate. Then the impact of Central Bank of Republic of the Turkey&rsquo / s (CBRT) decisions and actions on both the level of exchange rate and the volatility is investigated. Moreover the relationship between volatility and market liquidity is examined using spot foreign exchange (FX) market volume as a proxy. The results reveal that, in contrast to preceding findings, Student-t could not capture the leptokurtic property better than normal distribution does. Furthermore, an increase in Turkish government benchmark bond rates, CBRT FX purchase interventions and announcement of suspending/ decreasing-the-amount-of FX auctions lead Turkish lira to depreciate. Because of the significant positive leverage effect, the results of GARCH and EGARCH variance equations differ so much. Thereby the results should be evaluated cautiously. In addition it is observed that, only EGARCH model gives significant results when the spot market trading volume is included in the models

We present two option pricing models, both different from the classical Black-Scholes-Merton model. The first model, suggested by Heston, considers the case where the asset price volatility is stochastic. For this model we study the asset price process and give in detail the derivation of the European call option price process. The second model, suggested by Brody-Hughston-Macrina, describes the observation of certain information about the claim perturbed by a noise represented by a Brownian bridge. Here we also study in detail the properties of this noisy information process and give the derivations of both asset price dynamics and the European call option price process.

As the trading volume in TURKDEX, the first and only options and futures exchange in Turkey, increases, it becomes more important to have an understanding of the effect of stock index futures trading on the underlying spot market volatility. In this respect, this thesis analyzes the effect of ISE-National 30 index futures contract trading on the underlying stocks&rsquo / volatility. In this thesis, spot portfolio volatility is decomposed into two components and this decomposition is applied to a single-factor return-generating model to focus on the relationships among the volatility components rather than on the components in isolation. In order to measure the average volatility and the cross-sectional dispersion of the component securities and the portfolio volatility for each day in the sample period, a simple filtering procedure to recover a series of realized volatilities from a discrete time realization of a continuous time diffusion process is used. Results reveal that inception of futures trading has no significant effect on the volatility of the underlying ISE National 30 index stock market.

This thesis presents the modeling of credit risk by using structural approach. Three fundamental questions of credit risk literature are analyzed throughout the research: modeling single firm credit risk, modeling portfolio credit risk and credit risk pricing. First we analyze these questions under the assumptions that firm value follows a geometric Brownian motion and the interest rates are constant. We discuss the weaknesses of the geometric brownian motion assumption in explaining empirical properties of real data. Then we propose a new extended model in which asset value, volatility and interest rates follow affine jump diffusion processes. In our extended model volatility is stochastic, asset value and volatility has correlated jumps and interest rates are stochastic and have jumps. Finally, we analyze the modeling of single firm credit risk and credit risk pricing by using our extended model and show how our model can be used as a solution for the problems we encounter with simple models.

The primary purpose of this study is to test the effects of inflation targeting in Turkey in terms of providing stability in the financial system by lowering the volatility in the Turkish stock market. Although there are many factors other than monetary policy which can affect stock market volatility, this study examines whether the volatility due to monetary policy can be reduced by increasing the accuracy of investors&rsquo / expectations about the central bank&rsquo / s future actions. In the first part, a &ldquo / Volatility Analysis&rdquo / is conducted for three sub-periods including the pre- and post-periods of the implementation of inflation targeting in order to see whether the volatility in the Istanbul Stock Exchange changed over time. Second, an &ldquo / Announcement Effect Analysis&rdquo / is carried out by using the central bank&rsquo / s interest rate and inflation rate announcement dates in order to evaluate how investors&rsquo / expectations react to a change in these rates during period from 2002 to 2007. Finally, a &ldquo / Combined Analysis&rdquo / is done in order to examine the relationship between the returns in the Turkish stock market and the surprise caused by the realized interest and inflation rates being different from their expected values. The empirical findings about the level of volatility indicate that there is a decline in volatility of the Istanbul Stock Exchange returns when volatility is compared on a pre- and post-policy period basis. Also, it is found that the announcement effect was present, meaning interest rate announcements generally came as a surprise to stock market participants. However, this announcement effect has a notably decreasing trend from 2002 to 2007 which is another evidence of the inflation targeting regime&rsquo / s success at reducing stock market volatility. Finally, the &ldquo / combined analysis&rdquo / shows that CBT&rsquo / s power to effect stock returns and to direct investors&rsquo / expectations increases from 2002 to 2007.

In this study, the effects of opening trading mechanism and information flow on return volatility are examined in the Istanbul Stock Exchange. The change in the morning opening mechanism from a continuous auction to a call auction on February 2, 2007 and the extension in afternoon trading hours on September 7, 2007 provide unique opportunities in this respect. First, it is found that the call auction trading mechanism has a decreasing effect on the morning open-to-open interday volatility and morning intraday volatility for low-volume stocks but it does not have an obvious effect on the same type of volatilities for high volume stocks. Second, the study provides evidence that the increased information flow towards the end of the trading day increases the afternoon close-to-close interday volatility for high volume stocks while it does not have such an effect on low-volume stocks. Third, the overnight return volatility is decreased slightly with the extension of trading hours.

The upward movement in oil and food prices in the 2000s has triggered interest in the information transmission mechanism between the two markets. This research investigates the volatility spillover between oil, food, and agricultural raw material price indexes for the period January 1980 to April 2008. The results of the Cheung-Ng procedure show that variation in oil prices does not Granger cause the variance in food and agricultural raw material prices. However, there is bi-directional spillover between agricultural raw material and oil markets. Besides, it examines volatility spillover between maize, wheat, soybean, rice, and oil spot prices for the period January-1998 to February-2009. The results show that volatility spillover in oil returns leads fluctuations in maize, soybean, wheat, and rice returns in 3 months. In addition, there are bi-directional spillovers between oil and soybean returns, rice and wheat returns. This topic is essential for countries whose populations grow rapidly because forecasting of commodity prices plays an important role in instituting the economic policy. Also, understanding the dynamics of the economy leads to better economic policies. Thus, results are important for investors and policy makers interested in price shocks and transmission.

The purpose of this study is to analyze financial dollarization phenomenon in the Turkish economy since the beginning of 1990&rsquo / s based on Ize and Levy Yeyati&rsquo / s (2003) minimum variance portfolio (MVP) framework. Financial dollarization, steamed by unfavorable macroeconomic conditions and uncertainties, is revealed by the experiences of recent banking and financial crisis as carrying significant drawbacks such that it complicates economic policy implementation and contains the seeds of fragility for the whole economy as well. Although, considerable progress has been achieved in reducing inflation levels and sustaining macroeconomic stability, financial dollarization displays rather an enduring stance. MVP approach is based on optimizing the currency composition of financial contracts depending on the risk and the return profile of agents&rsquo / portfolios. According to this approach, financial dollarization is an increasing function of the inflation volatility and a decreasing function of the real exchange rate volatility. In line with this framework, financial dollarization in the Turkish economy during 1990-2011 period is studied by also considering other important macroeconomic risk indicators and it is tried to shed some light on the success of inflation targeting policy in dealing with dollarization phenomenon.

Financial data, such as daily or monthly maximum log return of stock price usually possess heavy tail and skewness properties. In this thesis, we consider stock price data of computer hardware and money center banks. Heavy-tailed distributions including Pearson type IV, Pearson type VII and stable distribution were fitted to the daily log return of the data sets, and goodness of fit were compared. For the monthly maximum log return, nonlinear threshold time series models were fitted with heavy tailed innovation distributions. In addition, the value at risk and volatility of the data sets are derived from the fitted distributions.

This article examines the hedging positions derived from the Black-Scholes(B-S) model and the GARCH(1,1) models, respectively, when the log returns of underlying asset exhibits GARCH(1,1) process. The result shows that Black-Scholes and GARCH options deltas, one of the hedging parameters, are similar for near-the-money options, and Black-Scholes options delta is higher then GARCH delta in absolute terms when the options are deep out-of-money, and Black-Scholes options delta is lower then GARCH delta in absolute terms when the options are deep in-the-money. Simulation study of hedging procedure of GARCH(1,1) and B-S models are performed, which also support the above findings.