The top four United States mobile carriers expanded their control of the US wireless market last year, a federal government report said on Thursday, once again finding the industry is highly concentrated as a result of continuing consolidation. The Federal Communications Commission's annual review of mobile industry competition found the two largest carriers, Verizon Communications and AT&T, together controlled around 70 per cent of both the nationwide market share based on service revenues and the most-prized type of radio airwaves.