International calling is growing strongly but, hardly surprisingly, free calling with Skype and its ilk is growing way far more strongly than the traditional paid-for variety.

Paid-for international telephone traffic grew 5 per cent in 2012, to 490 billion minutes. Much of this rise was due to developing country mobile phone uptake and also driven by steady reductions in international call prices. Even so, says Telegeography, the 5 per cent aggregate increase in call revenue is well below the magic 13 per cent increase that would be needed to make up for the steady price declines.

Meanwhile the use of OTT voice and messaging applications is increasing at a stunning pace. Cross-border Skype-to-Skype voice and video traffic grew 44 per cent in 2012 to reach 167 billion minutes.

Just Skype's year-on-year increase of nearly 51 billion minutes is more than twice the increase achieved by all international carriers in the world, combined, it says.

However, if Skype’s traffic were added to the volume of international phone calls, international voice traffic would have grown 13 per cent in 2012, in line with historical trends.

So voice is still growing at the same steady rate, it's just that most of it is now Skype.