Big data refers to data that are so large and complex that traditional methods of collection and analysis are not possible. The amount and variety of big data has increased exponentially over the past decade. 'Data exhaust' is one source, which relates to data produced passively as a byproduct of user interactions with a system, such use of a mobile phone service or Internet banking. Online information is another, giving an indication of human intent, emotions, and wishes by collecting the information contact in web content such as news and social media interactions (e.g., Facebook, blogs, twitter), and online search history. Data can also come from physical sensors such as satellite images and traffic information (UNDP 2013).