Productivity in education has lagged productivity in other sectors of the economy because teaching is so labor intensive. Where exactly in the typical classroom is there room for investment, let alone productivity improvement? More chalk? Prior to online education, the bottleneck though which productivity improvements had to pass was the teacher, and we know that improving teacher productivity is very difficult, which is why teaching methods haven’t changed in millennia. Online education vastly increases the potential for productivity increases because it greatly increases the size of the potential market. Bigger markets increase the incentive to research and develop new products (coincidentally the very topic of my TED talk.) A tool used to improve online education–an interface, an algorithm, a new teaching method–can be applied very widely, potentially world-wide, thus greatly increasing the incentive to invest in the education sector, perhaps the most important sector of the 21st century economy.
Addendum: Here are interesting comments from Joshua Gans.