Since the publication of the "History of Trade Unionism" (1894) by Sidney and Beatrice Webb, the predominant historical view is that a trade union "is a continuous association on wage earners for the purpose of maintaining or improving the conditions of their employment." Karl Marx described trade unions thus: "The value of labour-power constitutes the conscious and explicit foundation of the trade unions, whose importance for the [...] working class can scarcely be overestimated. The trade unions aim at nothing less than to prevent the reduction of wages below the level that is traditionally maintained in the various branches of industry. That is to say, they wish to prevent the price of labour-power from falling below its value" ("Capital" V1, 1867, p. 1069).