What has data ever done for us? Georgina Sturge, a statistician at the House of Commons Library and author of the critically acclaimed book Bad Data, explores the rich history of moments when the United Kingdom has measured itself - from the revolutionary first census of 1801 to modern concerns about technological surveillance. The condensation of an entire society into numbers has revealed hidden issues: did the cholera death map in Soho lead researchers to a deadly water pump? Florence Nightingale shocked Victorian society with her charts showing that disease was the hidden enemy of the soldier? The discovery that industries such as fireworks production were staffed almost entirely by women helped improve workers' rights. The census also uncovers people who have been excluded from the nation’s history. Records reveal the remarkable presence of runaway American slaves living in Leeds in the 19th century, and that in 1901 there were 600 professional Italian chefs in the United Kingdom. More recent data has for the first time recognized religion, ethnicity, and LGBT identity. Sturge also tracks those who resisted state attempts at recording - people who burned questionnaires, stripped in protest, and, in the case of 500 suffragettes, avoided the 1911 census by skating all night around the Aldwych skating rink. Filled with fascinating social details, The Sum of Us highlights the human stories etched in the vast interconnected dataset collected by the United Kingdom over two centuries. It provides a vital picture of not what we imagine we are - but what we really are.