Democratization and human development (HD) are inherently controversial processes, which are viewed in this dissertation as elective affinities. This means that both can be seen as mutually inclusive and potentially reinforcing. Contrary to standard modernization theory, both processes are intertwined in an endogenous relationship, hi principle, both have the same logic of inference: the promotion of individual freedoms and the expansion of well-being, both political and economic. The purpose of this dissertation is to analyze how democratization can promote HD and how HD can promote democratization. In order to substantiate this argument the analysis focuses on three interrelated propositions arguing that: (1) Democratization and human development processes can be considered as mutually enhancing and complementary. This elective affinity occurs via their multifaceted characteristics as well as through their individual attributes. (2) Democratization and human development processes sometimes go through identifiable critical junctures or turning points. These turning points are path-dependent but not deterministic. (3) There are strong reciprocal connections between HD and democratization that form two chains which reinforce one another cumulatively over time. This dissertation combines in a single study qualitative and quantitative research methods to explain the mutually enhancing relationship between human development and democratization processes. In addition to reviewing these interactions in general, the dissertation contains in-depth historical and contextual analysis of the Central American cases. In particular, it compares and contrasts Costa Rica and El Salvador, investigating the elective affinities of democratization and human development processes in identifiable stages of their turning points. The findings illustrate the benefits of method triangulation (i.e. paired-comparisons complemented with cross-country analyses) to explore the complementary features between both processes over time.