Google grabbed 66.4 percent of the search engine market through May, its greatest share ever, according to adjustments made by comScore.
The market researcher, whose methodology for calculating search engine metrics is being questioned by industry watchers, said that Yahoo's search share for the month was 16.6 percent, while Bing's share was 10.8 percent.
Those numbers are down quite a bit from comScore's April tallies, when it listed Yahoo at 17.7 percent and Bing at 11.8 percent. That's because it subtracts contextual shortcuts and slideshows from those search engines for April and May.
Bing and Yahoo have "been putting a ton of links on their popular homepages that are search queries disguised as content," according to Business Insider.
These accompany image slideshows, where each image appears automatically on a Webpage and generates a query. This pads the numbers for both search engines, which chomp share at Google's expense.
Without the adjustments, comScore puts Google's search share at 63.7 percent, Yahoo at 18.3 percent and Bing at 12.1 percent, which means the search engine has gained 4 percentage points since launching in June 2009.
Financial analysts are finding themselves hard-pressed to trust the comScore data. Broadpoint Amtech analyst Ben Schachter wrote in a research note June 10:
"Unfortunately, comScore's methodology/definitional changes may continue to impact the usefulness of its reported data.
"It is easy to make adjustments for May (based on the numbers provided), but understanding the baseline of comScore's 'core' search will only become less clear."
ComScore, admitting that it counts context-driven queries from Yahoo and Bing, said it is in the middle of making changes to its methodology for classifying and counting Web searches.
The research firm expects to employ them in time for its July data, set for mid-August release. However, the company said it will continue to "explicitly quantify context-driven search volume in our monthly release notes to clients."
In the meantime, the comScore number adjustments show Yahoo isn't out of the woods despite the search share gains from shortcuts and slideshows.
The company had lost search share for 13 consecutive months before turning on its shortcuts and slideshows in time for comScore's April search stats.
"Investors will likely need to see the financial results before giving the company credit for any gains or stabilization," Schachter said.
Meanwhile, Jefferies and Company analyst Youssef Squali said it remains to be seen if Microsoft's share will see any downward pressure in June resulting from the company's decision to discontinue its Bing Cashback program.
Yahoo and Microsoft are hard at work helping Yahoo cede its search infrastructure to the Bing search and search ad platforms, with expectations for Bing to power Yahoo by the end of the year.