The 1990s have witnessed a revival in economists' interest and hope of explaining aggregate and microeconomic investment behavior. New theories, better econometric procedures, and more detailed panel data sets are behind this movement. Much of the progress has occurred at the level of...

Microeconomic lumpiness matters for macroeconomics. According to our DSGE model, it explains roughly 60% of the smoothing in the investment response to aggregate shocks. The remaining 40% is explained by general equilibrium forces. The central role played by micro frictions for aggregate...