In the book by Brynjolfsson E., Saunders A., what does the authors say about what is productivity, its importance and in what ways does IT contribute to productivity gains?

Furthermore, what do they say about frontier research opportunities?

Reference:

"Wired for Innovation. How Information Technology is Reshaping the Economy."

Brynjolfsson E., Saunders A. (2013)

MIT Press. ISBN 9780262518611.