Intelligently allocating research effort and funds requires deciding whether to build on recent advances or on more established knowledge. When recent advances create superior opportunities for invention, their adoption as research inputs in the invention process promotes technological progress....

New ideas no longer fuel economic growth the way they once did. A popular explanation for stagnation is that good ideas are harder to find, rendering slowdown inevitable. We present a simple model of the lifecycle of scientific ideas that points to changes in scientist incentives as the cause of...