Thesis: From a broad perspective, this thesis aims at exploring the extent to which microeconomic heterogeneity shapes the trends and fluctuations of aggregate outcomes, by focusing on bank credit, productivity, and the interaction between these two variables.The first part of the thesis is motivated by the weakness of the total factor productivity (TFP) growth observed post-crisis in most developed countries. It examines the evolution and characteristics of resource misallocation in the French manufacturing sector before, during, and after the Great Recession. The inefficiency of the input allocation dampened productivity growth in the lead-up to the crisis. It also accounts for a sizeable part of the disruptions observed during the Great Recession, with the interplay between labor and capital misallocation playing a major role. On the other hand, the post crisis slowdown appears to be mostly driven by the sluggishness of the firm-level TFP growth, rather than by a worsening of resource misallocation.The second part of the thesis examines how the granular structure of the loan distribution in France shapes the cyclicality of aggregate bank credit lent to non-financial corporations. Microeconomic credit shocks affecting the largest borrowers largely drive this comovement, while bank individual shocks do not contribute significantly. It suggests that at the macro level mechanisms specific to the granular borrowers dominate both the effect of the financial frictions constraining smaller firms and the bank lending channel. The high level of concentration on the borrower side also affects bank liquidity flows: it leads credit line takedowns to be less diversifiable and more synchronized.The third part of the thesis relates input allocation to credit allocation. It suggests that the propensity of banks to lend to healthy firms was significantly reduced during both the 2007-2009 crisis and the Eurozone crisis. As bank lending shocks affect firm-level real outcomes, this reduction contributed to decrease the investment gap between high-quality and low-quality firms, thereby directing capital input towards companies that were more risky and less productive. The surge in capital misallocation observed in time of crisis may therefore reflect disruptions affecting credit allocation.