preference or more generally a demand shock. More recently two other explanations have been advocated: surprise changes in …

amplify and propagate a macroeconomic shock. We focus on the U.S. Great Recession of 2007-2009 and proceed in two steps. First … an aggregate shock, and it does so if the distribution features a sufficiently large fraction of households with very …

by a shock that does not affect productivity in the short run -- and therefore does not look like a standard technology … shock -- but affects productivity with substantial delay -- and therefore does not look like a monetary shock. One … structural interpretation we suggest for this shock is that it represents news about future technological opportunities which is …