The number of U.S. searches grew 55 percent in December 2005 over December 2004, according to data released by Nielsen//NetRatings.

The growth accounts for 5.1 billion searches conducted in December 2005, up from 3.3 billion searches carried out the previous December. During this time, the U.S. Internet user base increased by just 3 percent to reach 207 million users in the total digital media universe, which includes some non-active users. In December, the number of active home users registered at 143.8 million.

"The growth of search and the role of search in usage of the Internet has been astounding," said Ken Cassar, senior director of analytics at Nielsen//NetRatings. "When you look at search penetration, it's near 80 percent. The number of searches each person generates, it's high. It would be intuitive to say the numbers can't get any bigger than they are, but they've continued nonetheless."

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