WORLDWIDE mobile phone sales will increase slightly more than 4 per cent in 2012, the lowest annual growth rate since 2009, research firm IDC predicted on Wednesday.According to a latest IDC report, vendors are expected to ship a total of about 1.8 billion mobile phones in 2012, compared to 1. 7 billion units last year. IDC said the slow growth in the overall mobile phone market is due to decline in the feature phone market as well as sluggish global economic conditions.Global shipment of feature phone, a term used to describe low- end handset not seen as a smartphone, will drop 10 percent this year, as owners are holding on to their feature phones in light of uncertain job and economic prospects, IDC projected.  In comparison ,the smartphone market is expected to jump 38.8 percent this year, largely offsetting the feature phone shipment decline.Despite the decline in sales, feature phones will still account for 61.6 percent of the total mobile phone market this year, according to projections by IDC. "The mobile phone user transition from feature phones to smartphones will continue in a gradual but unabated fashion,” Kevin Restivo, an IDC analyst, said in a statement.Smartphone is an increasingly attractive option for a growing number of users, thanks to factors such as high carrier subsidies, falling selling prices and lower-cost data plans, IDC said. Among the competing smartphone operating systems, Google’s Android will remain the dominant one at least by 2016, though its market share will peak at nearly 61 percent this year, according to projections by IDC.