When Jerry Yang stepped into the Yahoo CEO seat vacated earlier this week by Terry Semel, analysts said his goal may very well be to move Yahoo away from its all-things-media evolutionary path, and return it to its roots in search. If that's the case, then Yahoo has its work cut out for it, if today's numbers from Nielsen/NetRatings are to be taken seriously.

While the Panama search technology has indeed helped Yahoo step on the accelerator pedal, the Nielsen numbers suggest Google has already found overdrive. While Yahoo continues to command the largest number of URL destinations by many estimates, including Nielsen's, Google handled a 56.3% share of all US-based Web searches conducted during May, gaining over 22 points in market share in just one year's time, and handling 44.9% more searches now than it did in May 2006.

Buried behind the headlines for these numbers is perhaps an even more staggering statistic: Just the top three US Web search providers (Google, Yahoo, and MSN Search/Windows Live Search) handled 80.5% more searches last month (4,033,277,000 by Nielsen's estimate) than they did in May 2005, and 40.6% more than in May 2006.

That's a steady growth pace for the US Web search industry of just over 40% annually. And Google alone now handled 17.8% more searches in the US last month than all the top three search providers combined in the previous year.

It isn't as though Yahoo has stayed still. By any rational measure, it's gaining popularity, now handling over a billion and a half searches from US Web users per month, which is 18.6% more than during May 2006, and a nice 21.5% share of all US searches. But Yahoo's share of US search traffic is about even with last year. It's at the borderline, with Google driving search growth.

Who's on the other side of the picture? MSN Search is only growing at a rate of 0.8% annually, which is just as stagnate as it has been. Even after Vista's launch, new users are not particularly compelled to try out Windows Live Search - and with Microsoft's recent investment in new tools and features, that's a problem.

AOL Search ranks at #4, despite much of the recent attention being paid to Ask.com on account of its ramped up advertising campaign. But AOL only processed 9.4% of the US search traffic of Google last month - still growth, but not by much. And after Ask.com, you might start wondering why Nielsen/NetRatings continues to track the top ten.