Report: 44% of AT&T customers are on unlimited plans that haven’t been available since 2010

People with a cellular plan that works for them tend to stick with it for a while, according to a new report from Consumer Intelligence Research Partners (via Business Insider). But for AT&T at least, no plan is proving as sticky as unlimited data. 44% of AT&T(s t) customers are on grandfathered unlimited plans — that haven’t been offered since 2010.
The report uses data from a survey of 500 people to estimate what proportion of subscribers to the big four carriers are on unlimited data plans. CISP’s survey, however, contradicts AT&T’s own numbers which state that “81% of smartphones are on metered plans.”  Aside from AT&T, of course, Sprint(s s) and T-Mobile(s tmus), both of which highlight unlimited data in their marketing, have 78% of their customers on unlimited plans. Verizon(s v) has the smallest proportion of unlimited plans at 22% of its customers, partially due to a less forgiving grandfathering policy which requires subscribers to give up their unlimited data when upgrading their device.
According to the report, Verizon makes the most money per subscriber because it has the highest proportion of its customers on shared data plans. CRIP states Verizon is presumably is able to charge more for the same amount of data across several devices, as evidenced by its estimated 14 percent of Verizon subscribers paying over $200 per month. But this is an oversimplification: Neither T-Mobile nor Sprint have traditional shared capped data plans — subscribers can add secondary data devices to their voice plan, but those devices often tap into a unlimited bucket of data. If Verizon is making more money per subscriber, it is because it is charging more for data, not because of how many devices that data can be used on.
But what the report makes clear is that once a consumer finds a preferred wireless provider, he or she tends to stick to it, especially if it has a perk like grandfathered unlimited data. Although AT&T’s official policy allows customers to upgrade their devices without forfeiting unlimited data, it does prefer to remove grandfathered data when a user upgrades to an LTE phone — so customers trading up their old 3G iPhones for the two most recent 4G models are presumably pushed to shed their unlimited plans. AT&T also reserves the right to migrate customers from the unlimited data plan to a tiered data plan as long as they provide one billing cycle of notice.
But AT&T generally lets its customers keep their grandfathered data. Even the 44 percent number is not unbelievable: there’s at least two Gigaom employees in the New York office currently carrying phones on a grandfathered unlimited plan. For AT&T, turning a blind eye to grandfathered data could be a great way to keep subscribers loyal in the face of innovative new pricing schemes from carriers like T-Mobile.
This story has been updated at 4:30 PM ET to include AT&T’s publicly announced numbers regarding devices on unlimited plans.