TeleGeography estimates that Skype’s on-net (Skype to Skype) international traffic grew 36 percent in 2013, to 214 billion minutes, a sign that the skype’s traffic volume increase is coming at the expense of traditional carriers. The forecast is inline with a slower growth in the international telephone traffic from fixed and mobile phones, which has recorded growth of an estimated 7 percent in 2013, well below the 13 percent average that carriers posted over many of the past 20 years.
According to TeleGeography Report, although the volume of international telephone traffic remains far larger than international Skype traffic, Skype’s minutes are growing much more rapidly. Skype added approximately 54 billion minutes of international traffic in 2013, 50 percent more than the combined international volume growth of every telco in the world.
Besides Skype, other messaging applications such as WhatsApp, Facebook Messenger, Viber, Line, Tango, Google Hangouts, and Samsung’s ChatOn, have been installed more than 100 million times from Google’s online Play app store, alone, according to the report.
The significant increase in Skype minutes signifies the growing widespread adoption of over-the-top (OTT) communications applications for mobile devices.
Increase in International Phone and Skype Traffic, 2005-2013 
Source: TeleGeography
“The rapid spread of OTT services is making life ever more challenging for international service providers, but the PSTN will not disappear anytime soon,” said TeleGeography analyst Stephan Beckert. “No other network comes close to matching the global reach of the PSTN. While Facebook has approximately 1.2 billion monthly users, at year-end 2013, the PSTN connected to just over 8 billion fixed and mobile subscribers worldwide.”
