In the last two decades, economics has witnessed a proverbial boom in the development of causal explanatory approaches to medium-term macroeconomic fluctuations. Building on the theory of real business cycles and its extension in New Keynesian macroeconomic models, a research program has emerged whose productivity is surpassed only by its mathematical rigor. However, the scientific discussion, which has been increasingly abstract and largely focused on formal-analytical questions, is simultaneously accompanied by a growing estrangement between theory and practice; the supportive role of theory for economic policy often gives way to a purely academic exercise devoid of empirical relevance. Against the backdrop of this new business cycle dichotomy.