Relational egalitarians hold what matters for justice is that all members of a society “stand in relations of equality to others.” The idea that all human beings are moral equals is widely shared: it underlies the Universal Declaration of Human Rights and many national constitutions. How will this norm be affected by the arrival of “big data,” the collecting and analysing of huge amounts of data about individuals? Internet companies and government services collect data about individuals’ activities, including geographic locations, shopping behaviour and friendships. Many individuals voluntarily share such information on social media, some also track their physical activities in meticulous details. Experts expect that “people analytics” – big data applied to the measurement of work performance – will have a revolutionary impact on labour markets.