It has long been assumed that new product innovations are typically developed by product manufacturers, an assumption that has inevitably had a major impact on innovation-related research and activities ranging from how firms organize their research and development to how governments measure innovation. In this synthesis of his seminal research, von Hippel challenges that basic assumption and demonstrates that innovation occurs in different places in different industries. Presenting a series of studies showing that end-users, material suppliers, and others are the typical sources of innovation in some fields, von Hippel explores why this variation in the "functional" sources of innovation occurs and how it might be predicted. He also proposes and tests some implications of replacing a manufacturer-as-innovator assumption with a view of the innovation process as predictably distributed across users, manufacturers, and suppliers. Innovation, he argues, will take place where there is greatest economic benefit to the innovator.