For the first time in history, the middle- aged make up the largest, richest and most influential segment in the country. A trillion-dollar economy has grown up feeding and fuelling their needs, whims and desires. Millions of federal and foundation dollars have been spent on scientific research into their habits, health, marriages, divorces, fears, and passions. Their concerns and counsel dominate the self-help shelves in bookstores, while their quotidian dramas flood Facebook and Twitter.

This book is a biography of the idea of middle age from its invention in the late 19th century to its current place at the centre of society, where it wields enormous economic, psychological and social power. Patricia Cohen's fascinating and revelatory book reports on cutting-edge science and chronicles the varying forces that shape our understanding of middle age today. She traces the different definitions of middle age - biological, psychological and sociological - and the different visions of middle age -- sometimes an influential, wealthy and satisfied figure, sometimes a paunchy, sexless and discouraged one. She also dismantles some of the most stubborn myths about the middle years, such as the midlife crisis and the empty nest syndrome.