The phrase 'diminishing marginal returns' is missing from this article. The essence of diminishing marginal returns is something like, "low-hanging fruit gets

The phrase 'diminishing marginal returns' is missing from this article. The essence of diminishing marginal returns is something like, "low-hanging fruit gets picked first"; problems that have a good ratio of effort in to reward out are preferentially attacked and so, over time, the average problem is harder to solve or has lower yields. One could argue that 'stagnation' is occurring not because absolute innovation (however you make up a way to measure it) is down but because the average real-economy impact of a unit innovation (in made up measure) is getting smaller.