ABSTRACT
This chapter elaborates on the variety of data sources. It discusses what kind of data sources can be distinguished and how all these data can be categorized, as well as how data should be processed and stored. Specific attention is paid to data quality, data cleansing, and missing values. Important suppliers of external consumer data are Experian, Acxiom, and Claritas. An alternative way to structure data sources is to make a distinction between structured and unstructured data sources. Another lens for discussing data sources is our breakdown by market, brand/product, and customer. Brand data have a limited scope in that they focus only on brands and their performance. Collecting these kinds of data, especially for the demand side, is a costly effort. The influence of big data on customer data can be found in the large internal, unstructured datasets that are being built up and that are more and more within the scope of the data analyst.
