One of the main issues that social scientists are trying to understand is the emergence of social diversity within a community. In this talk, I will present an interacting particle system model for the formation of social structures. Individuals advance their social standing by competing against those in lower classes and they decline due to inactivity. I will also present a model for the dynamics of single-elimination tournaments in which two teams compete and the loser is eliminated. I use these models to quantify competitiveness among teams in different major leagues and conclude that the British soccer is the most competitive sport while the American Football is the least competitive one.