The focus of this book is the monitoring and assessment of urban settlements. As such, it looks at the circumstances in which the majority of people around the globe are living. Apart from the remaining rural population, there is a considerable part of the global population that was forcibly displaced by natural disaster, conflict, or persecution. They are often forced to live in temporary or transitional settlements as refugees or internally displaced persons (IDPs, see more detailed definition in the next section). By the end of 2012, about 44 million people worldwide were considered as forcibly displaced due to conflict and persecution. They included 15.2 million refugees and 28.8 million IDPs (IDMC 2013).