In November, Yahoo and Mozilla announced a new partnership, which would make Yahoo the default search experience in the Firefox browser beginning with version 34, which was released in early December.

On Thursday, Merkle | RKG released its Digital Marketing Report for Q4 2014 (download page) looking at performance data and trends for Google, Yahoo, and Bing. It looks at a variety of aspects of search, but a section in the middle deals specifically with the effects of the Yahoo/Mozilla deal on paid search.

“We’re now able to assess the impact of the deal on Yahoo’s share of Firefox paid search traffic, which grew from 12% at the beginning of December to 30% by the end of the year,” it says. “However, digging deeper reveals that Yahoo’s share of Firefox 34 paid clicks has been in decline ever since the first big wave of updates in the second week of December. While the initial rollout saw Yahoo’s share rise to a peak of 43% on December 10th, that figure was just 36% by December’s end.”

“This is primarily the result of users switching the default search engine of their browsers back to Google, as shown by the corresponding increase in Google’s share of Firefox 34 paid clicks throughout the month of December,” the report says. “All in all, it appears the deal will move about 2% or less of total paid search traffic from Google to Yahoo. This is far less than the 10%+ of paid traffic that stands to be on the table if Safari default search were to change hands, which news outlets have reported is a possibility in 2015.”

Google has been showing concern about users sticking with Yahoo. It’s been showing Firefox users who visit its homepage a message saying, “Get to Google faster. Make Google your default search engine.”

On Wednesday, the company tweeted:

According to the Merkle | RKG report, Bing and Yahoo outpaced Google in paid search growth, not only because of the Yahoo Firefox deal, but also rapid growth from Bing Product Ads.

Images via Merkle | RKG, Google