Market Indices are a well known concept in finance and have a crucial role in professional and academic financial fields. Indexes have spread over the world developing a huge industry and hundreds of institutional investors, pension funds or investment banks use, follow and create market indexes. However, it is very difficult to find literature about indexing. This book provides a conceptual, theoretical and empirical study of market indexes: Foundations of indexing, biases regarding market indexes and strategies to avoid them, are presented as tools to be used by passive and active investors. This book also pays attention to Financial Ecology and Minimum Risk Indices as alternative approaches to traditional financial problems. The analysis should be especially useful to professionals in the Fund Industry, or anyone else who may be considering utilizing market indexes as their investment tool.