We often talk about the growth of smartphone adoption, but will the day ever come where there are no feature phones left? 

According to Asymco analyst Horace Dediu, that day could be as soon as 2015 in the US. An estimated 31m US mobile subscribers dropped their feature phones for smartphones in 2012. Thats an average of over 550,000 a week, a rate which hasnt changed much since 2009.

Looking at the change in userbase over the course of 2012, Android and iOS were the only mobile platforms which grew, gaining 23.3m and 16.3m users respectively. BlackBerry shed 6m users, Windows Phone 1m – but feature phones lost a whopping 31.3m users.

“Some of this switching has to do with demand for smartphone services but some of it is also due to a decreasing supply of non-smart devices,” said Dediu in a blog post. “The shelf space being allocated to smartphones is nearing 100 per cent, and with shrinking shelf space comes an accelerated decline in the product category. It may not come in 2013, and perhaps not by 2014, but it’s quite possible that by 2015 the last feature phone will make its appearance in the US. And as the US goes, the world will follow.”

Dediu examined the range of phones sold at a Wal-Mart store in the US, and found that smartphones outnumbered feature phones at a ratio of 20:7, with T-Mobile lagging furthest behind with five smartphone models versus four feature phones.