Informal work – family care, voluntary work, and undeclared or unregulated work – is a critical form of labor in today's economy, yet remains underanalyzed and examined. This volume develops a comprehensive conceptual framework of informal work and analyses systematically the relationship of formal and informal work. Using a coherent theoretical and methodological approach, this volume explores informal and formal work in six countries and contributes to our empirical knowledge of informal work and its different interrelations with formal work in various societies. A landmark study in the analysis of work, the book demonstrates how the relationship of formal and informal work is developing, how this can be explained in the specific context of the arrangement of work and welfare, and in which ways informal work possibly contributes to social integration and social cohesion.