AT&T (T 1.30%) and Verizon Communications (VZ 0.88%) are two of the world's largest telecom operators by almost any measure. They rank second and third in terms of market cap, behind only Chinese giant China Mobile (CHL). They rank first and second in terms of trailing revenue.

But they drop down a notch in terms of profitability. In fact, the American duo sport the two weakest EBITDA profit margins among the 10 largest global telecom stocks.

Slicing and Dicing the Telecoms | Create infographics.

China Mobile scores the industry's largest profit haul, despite lagging AT&T's and Verizon's sales by a considerable distance.

What gives?

The American near-duopoly also happens to rank among the least efficient capital structures. Only Telefonica gives AT&T a run for its money when it comes to crushing debt loads and profit-sapping interest payments. Next on the debt list? It's Verizon. The margin picture would look even bleaker if I hadn't chosen the industry-standard EBITDA measure here, since EBITDA backs out interest expenses.

Both Big Red and Ma Bell are run by high-quality management teams. They are, after all, two of the 30 blue chips tapped to represent America's finest businesses on the Dow Jones Industrial Average (^DJI 0.06%) index. You don't get there without proving your worth via decades of sustained success, and these two stocks have certainly helped pull the Dow higher in the smartphone era.

The secret sauce in China Mobile's recipe sits near the top of the income statement. The company reported just $15 billion in cost of goods sold over the last four quarters, leaving a lot of room for industry-standard operating expenses and generous profits. Verizon's $46 billion and AT&T's $55 billion COGS expenses put a much tighter cap on the bottom line.

China Mobile's lightweight cost structure may not be available to American businesses due to higher labor costs. However, some of the most profitable companies on this list also operate in high-cost geographies such as Japan or Australia. It seems like both Verizon and AT&T could stand to squeeze some more efficiency out of their bulky operations at this point. Perhaps an influx of Japan-flavored competition could spark a revolution in service quality and operational efficiency among American telecoms?