AT&T Mobility has now clarified which customers are subject to the wireless-data throttling I described last week, though it still isn't explaining exactly what happens to them, or give a good reason why - other than that they have the temerity to think that "unlimited data" means what it says.
The bottom line: If you use less than 3 gigabytes of data per month on your iPhone or a similar device, or less than 5 gigabytes on an Android that runs on the speedier LTE network, there are no limits on your unlimited data.
But go past those limits, and you'll be throttled until the start of your next billing cycle.
How severely? AT&T still isn't saying - though it's also still not disputing reports of a 99 percent drop in speeds. That may sound like an enormous reduction, but it's consistent with what T-Mobile has acknowledged doing to customers who pass the stated caps on its data plans: They still get data, but essentially at 2G speeds, not 4G. AT&T says its throttled customers will "still be able to email and surf the web." Presumably you'll recognize them as they stare blankly at nearly blank screens, or mutter curses at a mute Siri.
T-Mobile says it wants its throttled customers to consider moving to a plan with higher limits. AT&T implies that it wants them to move to tiered plans, and also that they're data hogs: In January, it says, "the top 5 percent of our unlimited data plan customers used an average of over 50 percent more data than the top 5 percent of customers on tiered plans."
Interestingly, that "50 percent more" statistic appears to conflict with 2011 data that I and others reported last week from Validas, a Texas company that reviews wireless bills for customers. But it's more likely just an example of how statistics can be spun.
Validas, which sampled more than 55,000 cell-phone bills, found that AT&T's unlimited-data customers used about 25 percent more data, on average, than customers on tiered plans.
So is usage really soaring? Maybe not. Validas' sample examined the top 5 percent of all AT&T data customers - about 41.5 percent of them unlimited-data customers. For its purposes, AT&T is comparing the top 5 percent of unlimited-data customers with the top 5 percent of customers on tiered plans - customers who face overage charges above prescribed limits.
However you slice the data, there's limited evidence that many people are grossly abusing the unlimited-data plans. Validas says the top 5 percent of AT&T's unlimited-data customers used an average of less than 4 gigabytes of data per month. Validas says just 0.7 percent of all AT&T smartphone customers used more than 5 gigabytes per month.
Data hogs? Perhaps they're just people who believe the word unlimited means what it usually does.
Here's AT&T's statement, provided via email: