Global revenues from outsourced Voice-over-IP services will double to approximately $20 billion annually by 2015, according to a study by IT industry watcher ABI Research.

Statistics published by ABI in September suggest that both managed and hosted IP-PBX will see large increases in investment by enterprises over the coming years.

ABI’s analysis noted that investments in VoIP services had run “counter cyclical” to the overall downward trend in IT investment witnessed throughout 2009, registering high growth due to the perceived cost savings of outsourcing communications technology. “The trend of companies outsourcing their communications infrastructure has taken off in earnest,” explained ABI senior analyst Subha Rama, “as enterprise decision-makers look for cost savings without having to compromise on features and functionality.”