When news broke this week that Facebook was going to pay $19 billion to buy a text-messaging company called WhatsApp that has about 450 million users around the world, many in the U.S.  asked themselves “What’s That?” And, why was it worth so much money to a mega social media company like Facebook with 1.2 billion active monthly users?

The fact that WhatsApp is better known outside of the U.S. was likely one of the big reasons for Facebook’s move. A median of 78% of mobile phone owners used their devices to send texts, according to a Pew Research Center survey conducted last spring in 24 emerging and developing nations. (One caveat is that while more than half of the people in each of the countries surveyed own a cell phone, ownership of app-capable smartphones pales by comparison).

Facebook is still the dominant social networking site, but its user growth in the U.S. has slowed.  In listing reasons why WhatsApp is potentially worth so much to Facebook, Forbes noted that Facebook has had difficulty getting traction in developing countries, especially in Latin American, India and Asia.

In our spring survey of emerging nations, at least seven-in-ten cell phone owners said they use mobile devices to text in six of seven Latin American countries surveyed. And eight-in-ten or more cell phone owners said they texted in four of five Asian countries surveyed.

Bruce Drake  is a former senior editor at Pew Research Center.