My dissertation consists of three chapters. In the first chapter, I summarize the literature on international labor flows and on international capital flows, investment, and demographic transitions. I start with a historical recount of seminal papers on international labor and capital flows. I then focus on high-income, high-skilled labor flows of free mobility areas and point to where traditional migration models fail to explain these flows, and on the investment and the demographic transition of Latin America which has not been systematically studied. In the next chapters of this dissertation, I address these two issues. The second chapter of my dissertation, joint work with Daniela Viana Costa, studies labor flows of workers with similar skill-level and across countries with similar income. This chapter revisits empirical evidence on migration within the European Union-15, disaggregated by occupation. We find that most workers are highly educated and that they move to countries where their type (occupation and education level) is relatively abundant among natives. This is at odds with traditional models of migration. We develop a model with external economies of scale that generates an agglomeration force in high-educated occupations. Our main result is that a country that is relatively abundant in highly educated labor force will attract foreign labor of the same type. We argue this model is more suitable to analyzing migration flows between countries of similar income level. The third chapter of my dissertation studies the behavior of investment during demographic transitions. In particular, I focus on the period of time where the working age to population ratio reaches its maximum, namely the demographic window. I document that in Europe, Asia, and Oceania investment rates are higher 15 years before and during the window than in other periods of time, whereas in Latin America they are lower. To understand the relation between investment and a demographic window, I build an overlapping generations model with demographic change and variable degree of financial openness. Within this framework, I conduct several exercises and counterfactuals involving potential drivers of the investment behavior. I find that the demographic behavior in conjunction with the region-specific financial openness, can explain the main pattern of investment for the demographic window in Latin America vis-a-vis Europe, Asia and Oceania.