Is U.S. Economic Growth Over? has been much discussed. Gordon argues that US growth has already slowed down and will slow further for various reasons including action on climate change. He describes the idea that rapid economic growth might be a once off event in human history as "audacious" (p2). But I think this is a commonplace idea in ecological economics. And slowing growth in the frontier countries is a common assumption in building business as usual scenarios for assessing climate change policies. On the other hand, it runs counter to the usual endogenous growth theory assumption that the rate of innovation continues to accelerate with growing world population. From this perspective it is a fairly radical idea that if true requires change to some theories.