Decomposition and Management of Market Shares of Manufacturer and Private Labels in the Grocery Trade.- Current State of Academic Discussion on the Competition Between Manufacturer and Private Labels in the Grocery Trade.- Foundations and Current State of Academic Discussion on Market Share.- Research Needs and Delimitation of the Study.- Method for the Decomposition of Market Shares.- Derivation of Hypotheses.- Data Basis and Preparation.- Empirical Study.- Discussion of Empirical Results and Practical Recommendations.- Discussion of the Method for Decomposing Market Shares.- Final Considerations.