International Science Community Association Research Journal of Recent Sciences 2277 - 2502 3 4 2014 April 2 The Relationship between Ownership Concentration and Information Asymmetry Considering level of Voluntary Disclosure of Firms Listed in Tehran Stock Exchange 40 46 EN ZolfaghariZaferani Rashid 1 Faculty of Education And Consulting, Roudehen Branch, Islamic Azad University, Roudehen, IRAN Haji AliakbariNeda 2 HosseinRezaeiDolat Abadi 1 Islamic Azad University, Persian GULf International Educational Branch, Khuzestan, IRAN AliReza Eghbali 2 HassanHeidarySoltan Abadi 3 EspananiHamid Reza 1 Department of Biology, Faculty of Sciences, Payam Noor University of Iran, Employee social security, Isfahan, IRAN Shirani Kobra 2 Department of Pharmacodynamy and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, IRAN Khalilian Saadat 3 Department of Biochemistry, Faculty of Biological Science, Tarbiat Modares University, Tehran, IRAN Sadeghi Leila 4 Department of Biology, Faculty of Sciences, Payam Noor University of Iran, Isfahan, IRAN YousefiBabadiVahid 5 Physiology Research Center, Isfahan Cardiovascular Research Center, Isfahan Cardiovascular Research Institute, Isfahan University of Medical AmraeaiEsmaiel 6 Bansal A. 1 Department of ECE, G.L.A. University, Mathura, UP, INDIA Agarwal R. 2 Department of EIED, Thapar University, Patiala, Punjab, INDIA Sharma R.K. 3 School of Mathematics and Computer Applications, Thapar University, Patiala, Punjab, INDIA Paria Mohammadiha 1 Dept. of Educational Administration, Faculty of Psychology and Social Science, Central Tehran Branch, Islamic Azad University, Tehran, IRAN Mahdi Shariatmadari 2 Fereshteh Kordestani 3 Bakht Azam 1 Department of Computer Science, Islamia College Peshawar, Peshawar, K.P, PAKISTAN Qureshi RashidJalal 2 Faculty of Computing, SZABIST, Dubai International Academic City, Dubai, U.A.E Zahoor Jan 3 Department of Pathology, Lady Reading Hospital, Peshawar, K.P, PAKISTAN TajAli Khattak 4 Jafar Omari 1 Fazlzadeh Alireza 2 Department of Accounting, Tabriz Branch, Islamic Azad University, Tabriz, IRAN MohammadrezaM. Nahidi 3 Economics and Management Faculty, Tabriz University, Tabriz, IRAN > Research Paper 2013 8 19 2014 April 2 The present study determined a measure to explain influence of ownership structure on information asymmetry considering voluntary disclosure. Samples included 104 firms listed in Tehran Stock Exchange. Results showed that ownership concentration positively and significantly influenced on information asymmetry of all firms; moreover, firm size negatively and significantly influenced on information asymmetry. For all the firms, managerial ownership and institutional ownership had negatively and positively significant influence on information asymmetry, respectively. In firms with low voluntary disclosure, ownership concentration positively but insignificantly influenced on information asymmetry; in firms with high voluntary disclosure, while, ownership concentration positively and significantly influenced on information asymmetry. In firms with low voluntary disclosure, managerial ownership negatively but insignificantly influenced on information asymmetry; in firms with high voluntary disclosure, while, managerial ownership positively but insignificantly influenced on information asymmetry. Results also showed that institutional ownership positively but insignificantly influenced on institutional ownership in firms with both low and high voluntary disclosure. Copyright@ International Science Community Association