Most Internet users don''t stop at just one search engine, but instead rely on two or even three to find the highest-quality hits, Nielsen/NetRatings said in its newest survey.

While Google users turned to a rival least often -- just 58 percent of Google searchers also fired up the search sites Yahoo or MSN -- even Google doesn''t have a lock on loyalty.

"All of the major search players, including Google, [must] recognize that they exclusively own only a minority of their users," said Ken Cassar, the director of analysis at Nielsen/NetRatings, in a statement on Monday. "This highlights an opportunity and a threat to all of the established players in the market, and underscores the importance of continued innovation in a highly competitive market that is anything but mature."

Yahoo and MSN users were even less loyal to their search site. Nearly 71 percent of those who searched at Yahoo also visited at least one of the other two sites, while 70 percent of MSN users did the same. The top second-place search site for both Yahoo and MSN users was -- surprise! -- Google. Yahoo shared 39 percent of its traffic with Google, MSN shared 33 percent of its.

Nielsen/NetRatings'' survey also reported that -- again, surprise! -- Google ranked as the number one site in search query volume during January.

During the month, Google handled 1.9 billion searches, 47 percent of the total run by Americans at work and home. In comparison, Yahoo did 868 million (21 percent) and MSN 523 million (13 percent) searches.

Those three sites account for more than 80 percent of all U.S. Web searches, said Nielsen/NetRatings.

"With more share than its two nearest competitors combined, Google sets the pace in the search business," said Cassar.