The initial period of growth in the consulting industry was triggered by the Glass–Steagall Banking Act in the 1930s, and was driven by demand for advice on finance, strategy, and organization. From the 1950s onwards consultancies not only expanded their activities considerably in the United States but also opened offices in Europe and later in Asia and South America. After World War II, a number of new management consulting firms were formed, bringing a rigorous analytical approach to the study of management and strategy. The postwar years also saw the application of cybernetics principles to management through the work of Stafford Beer.