Forty-two percent of Americans now have access to broadband lines at home, an increase of 16% this year, according to a new Nielsen/NetRatings report issued today. The report also found at 61% of active Internet users rely on broadband, an increase of almost 10% in the 12 months following August, 2004.

More than 17 million Americans have signed up for broadband since January, a trend likely driven by the lower cost of broadband services, particularly DSL from telephone companies. The major telcos, including BellSouth, SBC Communications and Verizon, have dropped their basic DSL prices under $20 a month this year, at least for introductory offers.

“Although broadband penetration among Internet users has long been on the rise, it was always amid speculation that the high cost of broadband would limit its widespread adoption,” said Charles Buchwalter, vice president of client analytics, Nielsen//NetRatings, in a prepared statement. “However, over the last year, carriers have responded to the growing demand for lower cost broadband, and all indications are that this trend will continue.”

The number of narrowband Internet users declined by 10% over between August 2004 and August, 2005, the report concluded. More than 54 million Americans, or 38% of active Internet users, still use narrowband access, however.