• by Laurie Sullivan , Staff Writer @lauriesullivan, February 7, 2012

Google's influence continues to wane a bit across the Internet when it comes to referral traffic, but as of January 2012, the company still remains the No. 1 traffic source for 23 of the top 30 Web sites that Citigroup Investment tracks across six vertical market segments. Sixteen percent of traffic to the sites comes from Google. By contrast, Yahoo at No. 2 and Microsoft at No. 3 account for 11% and 6% of traffic, respectively.

The findings come from Citi's Annual Net Influence Report. The investment firm has tested the influence of companies since 2010 by running a comScore Source of Entries analysis for the top five U.S. Web sites in major verticals: Media, Retail, Travel, Auto, Finance and Health. 

Considering the opposition that Google encountered acquiring for $700 million ITA Software, which provides flight data, the Travel segment remains one of the more interesting markets in which the company dominates as the leading source of Web traffic to sites. Across the five leading online travel Web sites, Google ranked as the leading source of traffic for three of the five, accounting for 14% of the traffic on average to the top five.

Expedia ranked as the largest source of traffic for Priceline and Orbitz, which highlights the extent of comparison shopping in online travel. "Google's influence appears to have expanded, with Google showing the largest share improvement at nearly 200 bps over the last three years," Citigroup Analyst Mark Mahaney, Neil Doshi and Rohit Kulkarni wrote in the report.

It gets better for Google. When analyzing the finance market segment, Google ranks as the leading source of traffic for four of the five sites, with eBay the primary driver of traffic to PayPal, according to Citi. The company accounts for on average 13% of the traffic to the top five sites. "In terms of trends, Google saw its influence share improve 290 bps, while Yahoo and Microsoft saw their influence shares decline," according to the report.