“It is a capital mistake to theorize before one has data,” Sherlock Holmes advises hisassistant John Watson in “A Scandal in Bohemia,” the first of Sir Arthur Conan Doyle’sclassic short stories pairing the duo. “Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” The wise detective’s words continue to ring true more than a century after the publication of Doyle’s work, in a world in which data is becoming increasingly prevalent inevery facet of our lives. “The world’s most valuable resource is no longer oil, but data,”declared The Economist in a 2017 opinion piece. Data is evidence, and evidence is criticalto businesses, governments, institutions, and individuals solving increasingly complexproblems in our interconnected world. Across a breadth of industries, the world’smost successful companies, from Facebook to Amazon to Netflix, cite data as the mostprized asset in their portfolios. United Nations Secretary-General António Guterrescalled accurate data “the lifeblood of good policy and decision-making.” Data powerseverything from movie recommendations to medical treatments, from supply chainlogistics to poverty-reduction initiatives. The success of communities, companies, andeven countries in the 21st century will depend on their ability to acquire, aggregate,and analyze data.