The recent energy price crisis and resulting inflation surge have sparked interest among researchers, policymakers and citizens in the cyclical nature of market power, defined as the ability of firms to raise prices beyond production cost increases. In my PhD, I will investigate the causal relationship between market power —often referred to as "greedflation" in popular media— and the U.S. business cycle, integrating insights from empirical macroeconomics and industrial organization. To do so, I will construct new quarterly U.S. economy-wide and sectoral indicators of market power, total factor productivity and creative destruction based on Compustat microdata. Building on these methodological contributions, I will assess how aggregate and sectoral U.S. market power responds to major business cycle shocks, such as technology, demand, and cost-push shocks, providing stylized facts for macroeconomic business cycle models. The granularity of the firm-level microdata further allows me to test the representative firm assumption typically made in these models by exploring the underlying firm-level distribution. Moreover, I will causally evaluate the effectiveness of several fiscal policy instruments in stimulating productivity and creative destruction, rather than entrenching market power. Finally, I will scrutinize how rising corporate market power throughout the cycle affects macroeconomic outcomes such as productivity, real wages, inflation and innovation.