Skype carried around 33 billion minutes of international voice calls last year, or around 8 percent of all international voice traffic, according to market researcher TeleGeography.
The growth in the company's international traffic - 41 percent in 2008 - has been remarkable, according to TeleGeography analyst Stephan Beckert, and has made Skype the largest provider of cross-border voice communications in the world, he said in a statement.
International voice traffic as a whole is also growing, although more slowly than for Skype. Last year it grew 12 percent, compared to 14 percent in 2007, according to TeleGeography.
The growth hasn't translated to more revenue for operators, however. They have to contend with declining call prices, which the move to Internet telephony services, including Skype, is partially responsible for.
As a consolation price wholesale operators including iBasis and Level 3 get to carry SkypeOut traffic, which lets users make calls from a PC to standard telephones. That service generated 8.4 billion minutes of calls in 2008, according to TeleGeography.
One explanation for the growth in minutes - despite the fact that the phone has to compete with, for example, instant messaging - is conference calling, according to Steve Blood, vice president in Gartner Research. Companies are putting the squeeze on air travel, and instead using conference calls to save money, he said.