This work brings three studies that evaluate public policies in Brazil. First, I study a recent infrastructure improvement program in São Paulo City, to estimate the causal impact of improved public lighting on nighttime crime. Secondly, I estimate the impact of immigrant influxes on local labor markets, taking advantage of a natural experiment generated by a massive wave of forced migration of Venezuelans to Roraima, a state in northern Brazil, from 2016 onward. Finally, I provide arguments to answer how new technology-based companies such as Uber impact traffic-related outcomes such as traffic deaths and accidents with fatalities.