This thesis consists of three essays on labor markets. The first chapter estimates the effect of the change in the Advance Notice Law in 2011 in Brazil. The new law made unjustified (without cause) dismissals more expensive for firms, and the cost gradually increased with tenure. Advance notice is part of the framework of employment protection legislation and is intended to preserve job contracts that, although undesirable in the short term, would be viable in the long term. However, results point to an increase in layoffs in the most affected firms and a higher turnover environment. These results are especially unfavorable considering the already high turnover rate in Brazil. I argue with a theoretical model that the design of the new law is consistent with the results because it increased not only the cost of dismissal but also the expected cost of continuity of employment. The second chapter evaluates the effects of the expansion of the ethanol mills in Mato Grosso do Sul (MS), from labor reallocation perspective. Tracking workers over the years, the analysis indicated mechanisms that enabled labor adjustment to the new labor demands generated by this large investment. I explore the reallocation across sectors, occupations, and regions. The third chapter estimates the impact of the modernization of agriculture (from the innovations of the 1970s) in Central Brazil, considering the effects on the labor force and investment decisions in education. The analysis shows that this event affected labor demand in the region, generating gains for the adult population. In this way, incentives have also changed for young people to make choices between working, with immediate job gains, and investing in human capital, and thus expect potentially higher gains in the future.