Google Inc enjoyed one of its biggest monthly gains in U.S. Web search market share in October, building on consistent gains over the past two years, according to industry data out on Wednesday.
Market research firm comScore Inc said Google's core Web search properties captured 58.5 percent of the U.S. market in October, up from 57.0 percent in September.
The top five providers of Web search all showed at least 5 percent growth in the number of searches in October. Yahoo Inc was number two after Google, followed by Microsoft Corp , IAC/InterActiveCorp's Ask.com and Time Warner Inc's network of sites, including AOL.
"They are all growing in the number of search queries but Google is taking a disproportionate share," comScore spokesman Andrew Lipsman said by phone.
Yahoo sites had 22.9 percent of the U.S. market, a 0.8 percentage-point fall from September. Microsoft slipped to 9.7 percent from 10.3 percent, Ask was flat at 4.7 percent and Time Warner's network dipped 0.1 percentage point to 4.2 percent.
Google shares rose more than 3 percent to a high near $670 before settling back later in regular Nasdaq trade to $666.51, up 2.8 percent. Yahoo shares fell 3.1 percent to $25.87, while Microsoft stock was off half a percentage point at $34.39.
On Tuesday, broker Credit Suisse set a $900 price target on Google, a new Wall Street high, arguing that the Silicon Valley Internet leader is poised to monopolize search.
Google attracted 6.1 billion searches of the 10.5 billion searches conducted by U.S. Web users last month. Total search activity grew 12 percent over September, which is typically a slow month until students return to school.
In recent months, comScore has introduced an expanded measure of search activity on major Internet sites including not just searches on, for example, Google.com but also searches on other Google properties such as video-sharing site YouTube.
By this measure, Google's Web search activity grew 14.8 percent, or faster than the single-digit growth rates of rivals Yahoo, Microsoft and Time Warner.
Search activity for News Corp's Fox Interactive Media dipped 1.8 percent, with its biggest property, social network leader MySpace, declining 1.7 percent. Comparable data for MySpace rival Facebook was not available in the survey.