eMarketer reports U.S. use of smartphones is catching up with the United Kingdom, one of the more advanced mobile markets in the world. eMarketer expects 65 % of U.S. mobile phone users, or 51.4% of the population, to use a smartphone at least monthly in 2014. That compares with two-thirds of mobile phone users in the U.K., or 53.7% of the total population. Among U.S. smartphone owners, Android-based handsets are the most popular.