Having covered the census as a major source of data on migration in Chapter 4, this chapter goes on to identify the gaps in data availability. Chapter 5 therefore describes in detail the different sources of internal migration available in the form of different sample surveys and how they supplement data on migration. While Chapter 4 covered the complementarity of the National Sample Surveys on migration with the Census of India, Chapter 5 describes the NSS as well as various other surveys available in India on internal migration, and what each of these surveys entails and how they can be used therefore to maximize information.