What did John Muth contribute to the business cycle theory?

John Muth contributed to business cycle theory through his formulation of the Rational Expectations Hypothesis in the early 1960s. He argued that individuals form their expectations about the future based on all available information and that these expectations influence economic decisions, thereby affecting business cycles. Muth's work shifted the focus from traditional Keynesian models, which often assumed adaptive expectations, to models that incorporate rational expectations, fundamentally altering how economists understand economic fluctuations. This approach emphasized the importance of information and expectations in shaping economic outcomes.