During the first half century after the publication of the books by Jevons, Menger, and Walras, capitalism underwent rapid change and experienced extraordinary turbulence. The first and most obvious change was the movement toward industrial concentration and giant corporations with worldwide trusts and cartels. The second change was the imperialist frenzy of the major capitalist countries. The third change was merely one of degree: whereas capitalism had always been an unstable economic system, constantly experiencing alternating periods of prosperity and depression, the length and severity of these depressions grew worse and culminated in the worldwide Great Depression of the 1930s. Combined with these changes, as well as with the chaos and social unrest that resulted from the increasing instability of capitalism, was the worldwide social turbulence that was manifested in the massive upheaval of World War I, the Soviet Revolution, and the emergence of fascism in Italy and Germany.