This book is a detailed and clear presentation of a surprising origin of macroeconomics. In Spain, 1916, Germán Bernácer (born in Alicante, 1883-1965) discovered and wrote about macroeconomics in his book Society and Happiness, Social Mechanics Essay. It was published, therefore, twenty years before John Maynard Keynes' work The General Theory of Employment, Interest and Money. In this book, moreover, later works of Bernácer are explained, up until 1955 when he constructed a gigantic scientific building of macroeconomy. Forewords by: PAUL A. SAMUELSON, ROBERT M. SOLOW, JUAN VELARDE FUERTES. Introduction: JOSÉ MARÍA FERNÁNDEZ PIRLA.