This thesis is about firm dynamics, and relates to the size and growth-rate distribution of firms. As such, it consists of an introductory and four separate chapters. The first chapter concerns the size distribution of firms, the two subsequent chapters deal more specically with high-growth firms (HGFs), and the last chapter covers a related topic in distributional estimation theory. The first three chapters are empirically oriented, whereas the fourth chapter develops a statistical concept. / <p>QC 20130215</p>