This thesis examines how economic forces shape the nature of employment and the development of human capital. Each of the three chapters in the thesis brings economic theory and causal inference to administrative data to better understand the mechanisms that ultimately determine people's livelihoods. Collectively, the chapters emphasize how imperfect markets and institutions have the powerful potential to either reduce or exacerbate existing inequalities. The first chapter identifies the effects of firms on the career advancement of blue-collar workers and interprets these effects through the mechanism of employer learning. I use administrative data on the universe of Brazilian formal employment to study vertical promotions from product...