In IQ: A Smart History of a Failed Idea, the first popular history of the intelligence test, Stephen Murdoch reveals how universal education, mass immigration into the U.S. in the early 20th century and the demands of mobilization in the First World War created the need to rank populations by intelligence. In the following decades, the tests were used to decide whether people could settle in a new country, whether they could reproduce, even whether they lived or died. What has only ever been a rough guide to ability has, through the seductive power of a single, all-explaining number, come to be seen as an objective and infallible measure of intelligence, even of human merit. One of the most startling aspects of the story is just how often the exams are still used today. IQ is published by John Wiley and Sons in the US and Duckworth in the UK.