Google's September U.S. search market share crept up to 66.1 percent from 65.4 percent in August, according to new data released from comScore Oct. 13.
Perennial No. 2 search player Yahoo, whose results are now powered by Microsoft Bing, slipped from 17.4 percent in August to 16.7 percent through September. This may be a continued trend if more users jump ship to Bing or Google.
Bing nudged up from 11.1 percent to 11.2 percent in comScore's count of explicit core search, which the researcher calculates by excluding user interface features such as slide shows and contextual links.
The former triggers a series of Web pages that count as clicks; in the latter, clicks are counted each time a user hovers over words in news stories.
Yahoo and Microsoft enjoyed some percentage points of growth at Google's expense when they began using such features in April.
ComScore eventually altered its methodology for July's count, providing separate statistics for explicit core search and total core search, which includes the slide show and contextual link e-queries.
For September, comScore tallied more than 16.0 billion explicit core searches. Google saw 10.6 billion searches, followed by Yahoo with 2.7 billion and Microsoft with 1.8 billion.
September was an interesting month as it marked the first time comScore counted Google's Instant predictive search technology, which renders search results as users type them in the box. The user doesn't have to hit Enter or click a link to see results.
ComScore regards Instant search results served the way it would a slide show or contextual link, counting it as part of Google's total core query count.
Any time a user hits Enter or click a link after using Google Instant, that query counts toward explicit core search total.
Query result pages without explicit user action, but with a pause of at least 3 seconds, will count toward total core search.
"We believe the speed and quality of Google Instant should allow users to find answers to queries more quickly, and possibly facilitate additional queries on related topics as 'predicted' or 'suggested' by Google," said Susquehanna Research analyst Marianne Wolk in a research note.