When the web was young, most websites were in English. This wasn’t exactly surprising. After all, the web first emerged in the United States in a big way and was its largest initial market.

Over time, of course, the web has come to bring the world closer together and in turn, give companies anywhere in the world opportunities global in size.

For many companies, that meant moving beyond the English language to reach customers and stakeholders in their native tongues.

Today, mobile sort of resembles that early web. Yes, you can find apps and mobile websites that aren’t in English, but by and large, the number of them that have been localized seems relatively small.

That soon may change, however, as iOS and Android adoption grows outside of North America. According to mobile ad network Flurry, that adoption is occurring quite rapidly.

In a blog post, it notes that in January 2011, over half (55%) of the app sessions it tracked across iOS and Android devices came from the United States. 28% came from the next nine most prominent countries in terms of usage, and the rest of the world was responsible for just 17% of app sessions.

Fast forward to October. The United States now accounts for less than half (47%) of iOS and Android app sessions. Sessions from the next nine countries have jumped to 31%, and the rest of the world’s share of app sessions has grown to 22%. Making the growth all the more impressive is that absolute sessions in the United States doubled during this period.

In other words, despite rapid growth in mobile app usage in the United States, other countries are growing so fast that the U.S. can’t hold on to its relative share.

Leading the charge is China. As Flurry notes, it has a population of 1,3bn people, and many of them are quickly coming to love mobile apps. How much? Between January and October of this year, Flurry has seen the number of app sessions in China grow by a whopping 870%. But it’s not alone: Argentina, Israel, India, Saudi Arabia, Brazil, Belgium, Thailand, Russia and Taiwan have all seen growth during that same period exceeding 325%.

This means one thing: localization will be more and more important to mobile app developers as the opportunities to court audiences outside of the English-speaking world explode.

Of course, it’s important to note that ‘localization‘ means far more than just ‘translation.’ Good localization always goes beyond words and looks at culture and local conventions. That may be even more important in the mobile space given the complexities that are often present in creating compelling experiences on devices that are at the same time intimate and somewhat limited.

The challenges and investments required to be successful globally as an app developer could be significant for many developers, but the rewards will no doubt be even more significant as mobile devices have the potential to reach far more consumers.