Excerpt: “How do you weigh the economic benefit of the thoughts in Bill Gates' head? The sand on a beach can be measured, but how do you calibrate the value of the idea that turned those silica grains into silicon microchips? Though they sound like questions from a Mensa parlor game, they’re actually from the work of economist Paul Romer, and his answers may just revolutionize the study of economics. A sage for the silicon age, Romer is upgrading the dismal science to keep pace with the digital revolution.

Excerpt: “Ideas are different. Ideas have special properties,” Romer says. While things such as land, machinery and capital are scarce, Romer argues that ideas and knowledge build on each other and can be reproduced cheaply or at no cost at all. In other words, ideas don’t obey the law of diminishing returns – where adding more inputs like labor, machinery or money eventually results in the trailing away of additional output.