There is currently no consensus over a standard definition for paradata. Couper (1998) was the first person to introduce the term “paradata” to the field of survey methodology. He initially used the term to refer to automatically generated process data, such as the audit trails produced by Blaise. Since then the term has expanded to cover all types of data about the process of collecting survey data such as interviewer call records, length of interview, keystroke data, interviewer characteristics. Although interviewer observations and information from interviewer questionnaires do not describe processes, this kind of information is also often referred to as paradata. Not included under the term paradata are the actual survey questionnaire data. For the purpose of this review we also do not include metadata and auxiliary data under the term paradata.