Comcast and Time Warner Cable are dominating the market for new wireline Internet subscribers in the US, with AT&T and Verizon lagging far behind.

Cable already had a majority of the broadband market, even when you count slow DSL as "broadband," and that majority is growing.

"Comcast and Time Warner Cable led the growth in US broadband subscriptions during the third quarter, adding a combined 552,000 new subscribers," Strategy Analytics wrote last week. "Overall, cable operators in the US added 804,000 subscribers. However, the total number of US broadband subscribers only increased by 679,000 due to losses in DSL and slower growth in Fiber subscriptions at AT&T and Verizon. Over the past twelve months, Comcast and Time Warner Cable have accounted for 71 percent of the 3 million new broadband subscribers."

Among the 19 US Internet providers tracked by the research firm, Comcast alone accounted for 42 percent of new subscribers in the past year.

AT&T lost 129,000 Internet subscribers in the most recent quarter, bringing its total down to 15.8 million, while Verizon gained 2,000 customers for a total of 9.2 million, reported Leichtman Research Group, which tracks the 17 largest cable and telephone providers in the US, covering 94 percent of the market. Cable companies added 787,629 Internet subscribers in the third quarter, boosting their total to 54.3 million. Telcos offering DSL and fiber service lost 143,338 Internet subscribers, bringing the segment down to 35.2 million.

Comcast had 22.9 million broadband customers at the end of the quarter, while TWC had 13 million. Charter, which is trying to buy Time Warner Cable, added 147,000 subscribers in the quarter to boost its total to 5.4 million.

Cable's continued strong performance isn't surprising, as US consumers generally have few high-speed Internet options and cable easily outperforms DSL Internet. Under the latest federal definition of "broadband," which requires speeds of 25Mbps down and 3Mbps up, Comcast alone has more half of all US broadband subscribers. The market share stats from Strategy Analytics and Leichtman include services that offer slower-than-broadband speeds.

Fiber could pose a threat to cable, and AT&T plans to deploy its fiber service to 12.5 million potential customers. But Verizon is almost done expanding its fiber network, having resisted pressure from government officials in New York City and other cities who say the telecom hasn't lived up to deployment promises.

Verizon said it added 114,000 fiber Internet subscribers in the most recent quarter, down from 162,000 adds a year ago. AT&T didn't break fiber-to-the-home out separately in its earnings report, but it said it gained 172,000 subscribers in "IP broadband," which includes fiber and most of its DSL customers.

Verizon is selling its DSL and fiber facilities in three states to Frontier Communications, but the transaction hasn't been finalized.