Innovation and technological change are important drivers of economic growth. There is strong evidence that various types of innovation, whether they differ by source, goal, or field, have differing implications for economic outcomes. These arise primarily because of differences in the level of associated externalities (spillovers) and in the ability of innovators to internalize the public benefits from these activities (appropriability). In my research, I focus on identifying the nature and magnitude of these spillovers. Additionally, building on recent advances in the structural modeling of firm incentives, I quantify the extent of appropriation by innovators, particularly as it varies across innovation types. This allows one to provide a detailed accounting of misallocation in the economy and consider policies which can alleviate this. In the first chapter, entitled "Technological Interdependence", I study theoretically and empirically how the level of interdependence between new and old technology affects firm dynamics and the incentives for innovation. In the second chapter, entitled "Back to Basics" (joint work with Ufuk Akcigit and Nicolas Serrano-Velarde), we propose and utilize a novel strategy for quantifying the spillovers associated with basic research as they differ from applied research. Finally, in the third chapter, entitled "Transition to Clean Technology" (joint work with Daron Acemoglu, Ufuk Akcigit, and William Kerr), we construct and estimate a joint model of the climate-economy system and investigate the effects of various carbon policies.