An economist argued ideas don't run out the way resources do, so growth needn't stop

Standard growth models assumed economies eventually hit diminishing returns as they pile up machines and buildings. Paul Romer argued that knowledge behaves differently: one firm using an idea doesn't use it up, so ideas can keep compounding and driving growth indefinitely. The insight, built into what's called endogenous growth theory, won him a Nobel Prize in 2018.

— Paul Romer, Endogenous Technological Change — Journal of Political Economy, 1990