Acknowledgements

I am very grateful to my supervisor Professor Pertti Haaparanta for his guidance and encouragement without which I could never accomplish the job with my thesis. I am also grateful to Professor Tapio Palokangas who took supervising responsibility at a crucial stage of my thesis and provided me the necessary suggestions. Then my heartiest gratitude goes to the pre-examiners of the thesis, Professor Paavo Okko and Dr. Marko Korhonen, whose comments greatly helped me to improve the thesis. This thesis has been written during the time I have been at Economics Department of Helsinki University as a graduate school fellow of the Finnish Doctoral Program in Economic (FDPE) and as a scholar fellow of Yrjö Jahnsonn (YJ) Foundation. I thank both the FDPE and YJ foundation for giving me the opportunity to concentrate exclusively on my doctoral studies, and the Economics Dept for its arrangement of working room with necessary research equipments. In this regard I am very thankful to Professor Vesa Kanniainen for his cooperation to get position at the Dept and to get FDPE fellowship, and for his all time fruitful comments. I would also like to thank Professor Mika Linden and Professor Anne Mikkola for their time worthy instruction