300px Riemann Zeta Func40% last two years, 30% expected next two years. NBN Chief Bill Morrow sees the Netflix surge passing and future growth slowing. The average NBN user draws 131 gigabytes/month, reports Geoff Long at CommsDay. (Not linkable. CommsDay is an excellent news source, available only via a professionally priced subscription.) 

Until two or three years ago, landline data traffic for the average user had been growing at 40% +-5% for a dozen years. Fortunately, Moore's Law has brought down the costs of the necessary components at a similar rate of about 40%. The marginal cost per subscriber per month has stayed flat at all the large carriers: About $1/subscriber/month across the developed world. Wireless growth has been similarly slowing.

Andrew Odlyzko produced the most reliable data, with Cisco data confirming for more recent years. From 2002 to 2009, Odlyzko found a median growth rate of 43% and a mean of 51%. Adjusting for the number of Internet users yields a trend of 35% to 45%. Recently, company reports have been variable but are trending lower. 

A good thing, because Moore's Law seems to be slowing down.

Odlyzko is also a world class mathematician. His work on the Riemann Zeta function (hllustrated) is in the textbooks and was crucial to the proof of Fermat.