Broadband penetration in the U.S. jumped 31% in the first half of last year, according to the latest figures from the FCC. The Commission reported Monday that the nation added 8.8 million "advanced services" lines during the first six months of 2005 to reach a total of 37.7 million lines on June 30. The FCC defines advanced services lines as those that deliver broadband speeds of more than 200 kbps in both directions. The agency distinguishes advanced services lnes from high-speed lines, which deliver speeds of more than 200 kbps in one but not necessarily both directions. Using that second definition, the FCC estimated that the U.S. had 42.9 million high-speed lines at the end of June, up 13% from 37.9 million at the close of 2004. No matter which way you slice broadband, cable modems continued to dominate the field in the first half of 2005. The Commission said cable modems accounted for 61.0% of the 42.9 million high-speed lines on June 30, while DSL accounted for 37.8%. It also said cable modems accounted for an even greater 64.9% of the 37.7 million advanced services lines at the end of June, while DSL accounted for 34.4%.