This is an MIT Sloan Management Review article. New research finds that stories about consumers'positive experiences with a brand significantly increase users'engagement with brand websites, and stories originating from consumers are especially powerful in shaping brand attitudes in social media. Indeed, companies that aren't offering experiences that leverage consumer input in brand-related narratives are missing out on important opportunities to connect in a meaningful way with potential buyers.

This article illuminates the drivers of exponential improvements in performance and cost and explains why some technologies experience more rapid improvements than others. It shows how exponential improvements in performance and cost are largely driven by two mechanisms: creating materials to better exploit their physical phenomena; and geometric scaling. Improvements in some technologies are directly experienced through these two mechanisms, while improvements in higher-level "systems" are indirectly experienced through improvements in specific "components." Understanding these drivers can help us better recognize when new technologies might become economically feasible and thus create appropriate policies for promoting improvements.