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We identify an inflationary technology news shock as the leading source of business cycle variations for the postwar U.S. economy. This shock acts like a demand shock: it induces strong positive comovement in real quantities - GDP, consumption, investment - and weak positive comovement between real quantities and inflation, contrary to the view that anticipated technological innovations reduce inflation. The technology news shock became the predominant source of the business cycle after the 80's. The reason is that anticipated improvements in future technology lead to improvements in financing conditions. The monetary policy response to these anticipations is contractionary in the short run, independently of the sample period. However, the response is more short-lived after the 80's than before and with respect to other non-technology shocks. Finally, the inclusion of sentiment, uncertainty and TFP measurement error shocks does not affect the importance of the technology news shock.
