Effects of changes in micro-structure of Borsa İstanbul on the intraday returns and volatility and closing prices

Closing price manipulation has been tested and intraday pattern has been analyzed in Borsa Istanbul using 102 shares in different indexes while focusing on the period between November 1, 2006 – May 31, 2012. Additionally, an investigation of the implementation of opening call session, abolishing transmitting orders on a floppy disk, reduction of price tick size, allowing order cancellation and implementation of closing call session in the micro structure to intraday pattern of Borsa Istanbul is carried out covering the same period of time. Due to two seperate trading sessions, the intraday return pattern fits the double U form more precisely the W form and is in fact consistent with the literature. When compared to other time periods in trading session, the returns are higher both in the opening and closing times. Due to two seperate trading sessions, the votality pattern fits the double L form. It has been identified that the volatality is high during the opening time and it decreases towards the end of the session. Implementation of opening call session decreased return meanwhile increased volatility during the opening time. Implementation of closing call session decreased the return in the closing time and the volatality in the opening time of the next morning. According to Felixson and Pelli (1999), there were uprise closing price manipulations until the implementation of closing call session in Borsa Istanbul. This uprise closing price manipulation seems to have been significantly eliminated after the implementation of closing call session. Estimating quite high, positive and high significance level of coefficient of net position (upto last 15 minutes of second session) to total trades supported that there is uprising closing price manipulation. The observations show that the implementation of closing session had definite impact in eliminating the uprise closing price manipulation.