The thesis deals with five different human capital-related problems and tries to approach these problems from an empirical point of view. Each essay includes an own introduction and a short conclusion. All parts of the thesis are self-contained and can be read separately. The first essay entitled \"Size matters. The Relevance and Hicksian Surplus of Preferred College Class Size\" deals with the impact of class size on student evaluations of instructor performance using a sample of approximately 1,400 economics classes held at the university of Munich. Secondly, the data of a representative survey is used to estimate the willinngness-to-pay for preferred class size. Based on these findings and data, we try to give some evidence on w...