If sales volume were equal in all years (and they are not), then you might say about $75 billion a year is the global revenue for all consumer and business VoIP and UC-related services.
The global telecommunications industry represents about $2.1 trillion in annual revenue, according to The Insight Research Corporation.
Insight Research expects global revenue will grow from $2.1 trillion in 2012 to $2.7 trillion in 2017 at a combined average growth rate of 5.3 percent.
NTT, leader of residential VoIP market, topped 14 million subscribers in the second quarter of 2012, according to Infonetics Research.
Roughly 15 percent to 20 percent of all new IP PBX lines sold are part of a managed service or outsourced contract, making managed IP PBX the largest segment of business VoIP services.
SIP trunking revenue grew 23 percent in the first half of 2012 compared to the second half of 2011, led by strong activity in North America, Infonetics Research estimates.