For two decades, international calls — made through traditional phone companies — had been growing at a clip of about 13 percent a year. Then things hit a speed bump.

“We saw about 9 percent growth in 2011 and estimate about five percent growth in 2012,” says Stephan Beckert, an analyst at the research and consulting firm TeleGeography.

Meanwhile Skype’s international calls grew about 45 percent. Beckert estimates that Skype handles about one-third of the international calls being made today.

Charles Golvin, an analyst at Forrester, says international calls were once a high-profit business for traditional phone companies but today, “it’s a small part of their business, they don’t feel the pinch.”

Golvin says phone companies have moved onto data. Selling data plans for smartphones is a growth spot for companies like Verizon and AT&T.

And as more Voice-over-Internet calls, like the ones made on Skype, move from the desktop to the smartphone — that means selling more data — and the phone companies will make out just fine.