Aggregated productivity is the primary source of long-run economic growth. Therefore, understanding the nature of productivity accumulation is crucial to promoting welfare and development across nations. Recent literature has turned to the micro-foundation of aggregated productivity by studying the role of firms and entrepreneurs in shaping this process, which is the focus of my dissertation. This dissertation consists of three chapters, each of which investigates how heterogeneous firms\u27 decision making determines aggregated productivity. The first chapter studies the role of the financial system in selecting and developing the most promising business plans. In particular, more developed financial sectors are able to better allocate res...