But the picture of a leader, a runner-up and two also-rans is more complicated than it seems. A saturated market with fewer new customers to compete for means that the big four's relative positions in terms of size are increasingly stratified.
This makes ARPU a more important metric than ever, as extracting the most value from existing customers becomes paramount. Who's doing the best job at that, however, is less clear, as some of the big four have begun using alternative metrics to put the best possible face on their financial results.
Verizon
Big Red provides a metric called ARPA, or average revenue per account. That's a subtle but important difference -- for a company that's big on family and small business group plans, the number is likely to be a lot higher than it would be if revenues were measured on a per-user basis.
Verizon's high price point also isn't hurting its revenues, though it might be hurting its customer base in the long run. The company's unwillingness to engage in a price war with competitors like Sprint and T-Mobile may be costing it small numbers of subscribers, according to a report from Bloomberg.
T-Mobile
T-Mobile takes a different approach, reporting average billings per user, rather than average revenue. Once again, it's a small but important shift, according to IDC senior research analyst Brian Haven.
"ABPU is a more favorable metric for someone like T-Mobile, who offers a more 'economical' wireless option because it doesn't incorporate the revenue margin -- it just looks at the how much the carrier is charging per user," he said.
Sprint and AT&T
Sprint reports a standard ARPU metric in its quarterly earnings filings. That may be part of the reason why the company's stock is so much lower than those of its competitors -- ARPU is down across the market in general, according to Haven.
"[That's] more telling of how the overall market is changing as opposed to the subjective performance of any one carrier," he said.
AT&T's numbers bear this out -- its ARPU figure is considerably higher than Sprint's, but still show a general decline over the past several quarters.