A joint study by Fierce Wireless and NPD Connected Intelligence has been tracking data usage of Android (and now iOS) users across the big four carriers in the states. Shown above is the chart of the average data usage of the tracked users over the last 6 months. T-Mobile (after a short drop) and AT&T have both been trending upwards, while Verizon and Sprint (strikingly so) have been trending consistently downwards. Average usage in September was 1.09, 0.89, 0.57 and 0.68GB on T-Mobile, AT&T, Verizon and Sprint, respectively.
T-Mobile offering unlimited data is enough to explain the increase in usage, and AT&T has started to move to generally data-friendly shared plans as well. It's interesting to see Verizon data usage going down considering its expansive rollout of LTE, but let's also remember nearly all recent Verizon phones have software built-in to
force help users choose Wifi more often. Sprint as of late is well-known for extremely slow 3G data speeds -- and the LTE network isn't really there yet -- so it's not surprising to see data usage trending downwards on the Now Network.