Verizon Wireless has the largest average bill size among the four major mobile carriers in the US, while T-Mobile has the lowest, according to a survey released on Tuesday by research firm Cowen and Company. The survey of 1,876 US-based mobile customers in Q4 2013 pegged the average monthly Verizon bill at $148, higher than Sprint ($144), AT&T ($141), and T-Mobile ($120). The numbers reflect postpaid subscribers and include all taxes and fees. They include both single users and family plan customers. Across the industry, 68.5 percent of postpaid respondents were paying for family plans, with 26.1 percent on individual plans and 5.4 percent on corporate plans. Verizon had the most family and corporate plans, with 72.3 percent of respondents paying for family plans and 7.0 percent on corporate plans. The report did not break out the average individual bill size by carrier.