Smartphones are taking an increasing percentage of the total number of mobile devices sold in the worldwide market, according to a new report from market research firm Gartner. According to the study, Smartphones will account for 14 percent of the total number of mobile devices sold worldwide, up 23.6 percent over 2008. Gartner predicts that number will increase to 38 percent by 2013.

While the numbers look good for the devices, Gartner warms that carriers could affect the growth of the smartphone category.

“This positive outlook could be negatively impacted by mobile operators’ decision to associate all smartphones with high flat-rate data plans, which could increase the total cost of ownership beyond mass-market consumer acceptance,” the report reads.

Overall, worldwide mobile device sales reached 1.2 billion units, a slight decline of 0.67 percent from 2008. Gartner predicts that in 2010 mobile devices will show an increase of 9 percent.

Gartner also said that an increase in the sales grey market devices will affect Nokia’s market share the most.