Google increased its lead against nearest rival Yahoo in search engine usage during November, according to comScore Networks.

Google nabbed almost 40 per cent of all US searches, a 10 per cent lead.

Google increased its share of searches by 5.2 per cent compared with November 2004, while Yahoo saw its share shrink by 2.5 per cent, the market researcher said.

Overall, US residents conducted 5.15 billion searches in November, up 9 per cent. Google's search sites processed 2.05 billion of those searches, or 39.8 per cent, followed by Yahoo sites with 1.52 billion, or 29.5 per cent.

The story in November 2004 had been much different, with Google holding a much smaller lead over Yahoo. Back then, Google had a share of 34.6 per cent to Yahoo's 32 per cent.

Search engine usage is the motor behind the largest type of online advertising, paid search, in which ads are delivered along with search results. Most of Google's revenue is generated by paid search advertising. Yahoo and Microsoft have invested heavily on search technology in recent years to capitalise on the robust growth in paid search advertising.

Microsoft held on to third place but its also slipped and its share fell from 16 per cent to 14.2 per cent. Time Warner which includes AOL, came in fourth place with 8.7 per cent, down from 9.1 per cent. Finally, Ask Jeeves, which is owned by InterActive, took the fifth spot and increased its share by 1 per cent to 6.5 per cent, according to comScore.