during the upper turning-points of the periodic global long cycles of boom and bust known as Kondratieff waves. Such waves of proletarian insurgency, claims Screpanti, were global in reach, saw workers breaking free of the dynamics of the capitalist system, and aimed to overthrow that system. According to van der Linden and Thorpe, workers' radicalization manifested itself in their rejection of the dominant strategies in the, mostly socialist, labor movement, which was led by reformist trade unions and socialist parties. Lenin posited that "revolutionary syndicalism in many countries was a direct and inevitable result of opportunism, reformism and parliamentary cretinism." A feeling that ideological disputes were draining workers' power led Dutch, French, and American syndicalist organizations to declare themselves independent of any political groups. In countries like Italy, Spain, and Ireland, which was still under British rule, parliamentary politics were not seen as a serious means for workers to express their grievances. Most workers were disenfranchised. Yet even in France or Britain, where most male workers had the right to vote, many workers did not trust party politics. The enormous numerical growth of well-organized socialist parties, such as in Germany and Italy, did not, in the minds of many workers, correlate with any real advance in the class struggle as these parties were thought to be overly concerned with building the parties themselves and with electoral politics than with the class struggle and had therefore lost their original revolutionary edge. The socialists preached the inevitability of socialism, but were in practice bureaucratic and reformist. Similarly, the trade unions frequently allied with those parties, equally growing in numbers, were denounced for their expanding bureaucracies, their centralization, and for failing to represent workers' interests. For example, between 1902 and 1913 the German free trade unions' membership grew by 350% but its bureaucracy by more than 1900%. Another common explanation for the rise of syndicalism is that it was a result of the economic backwardness of the countries in which it emerged, particularly France. Newer studies have questioned this account. According to van der Linden and Thorpe, changes in labor processes contributed to the radicalization of workers and thereby to the rise of syndicalism. This rise took place during the Second Industrial Revolution. Two groups of workers were most attracted to syndicalism: casual or seasonal laborers who frequently changed jobs, and workers whose occupations were becoming obsolete as a result of technological advances.