Biased news. These numbers take into account only subsidized smartphones, but a lot of people buy carrier-free smartphones in stores.
In my case, for example, I never buy subsidized phones in Brazil. In USA I presume the same happens.
I dont know the numbers but I dont think the market for un-subsidized phones in the US is very big. Most people wait for their two years to be up before they buy the next subsidized phone. The monthly contract is the same whether or not you get the cheaper phone so there is not much reason to pay extra for a full-price phone. Of course, there are some that pay the full price but I think it is pretty small and usually because they want a new phone before the contract lets them get a subsidized phone.