What People Really Think About Search Engine Ads. (You Might Be Surprised.)

Insights by Stanford Business, March 7, 2024

by Theodore Kinni


iStock/Nuthawut Somsuk

Revenues from search ads are expected to exceed $300 billion in 2024 — making search the world’s largest advertising channel online or off. The ads are essential to search companies, but their value to users, who collectively make more than 1.2 trillion queries per year on Google alone, has always been something of a mystery.

Some experts argue that search ads are intrusive and even scammy — a distraction users must tolerate in exchange for free access to search engines. Others see the ads as a convenience, enhancing the search experience by offering users additional information and easy access to products and services related to their interests. “The utility of search advertising has been a controversial question and people have written positive and negative points of view on it in the media for a long time,” says Navdeep Sahni, an associate professor of marketing at Stanford Graduate School of Business. “But it is a question that needs to be answered with data.”

Sahni now has that data. Sahni and Charles Zhang, PhD ’22, then a GSB graduate student focused on quantitative marketing, got it from real users and real ads in a large-scale field experiment on a widely used U.S. search engine. While there has been copious research on the efficacy of search advertising for ad buyers, this experiment was unique for its scale and empirical focus on the value of ads to search users.

Collected over a period of five months in 2017, the data reports on queries submitted to the search engine by nearly 3 million unique users. For two months in the middle of the experiment, half of the users saw search results that included the usual number of ads that appear among the top results and in the middle of the page, known as mainline ads. “Whenever there’s a search query,” Sahni explains, “search engines use a proprietary algorithm that scores every ad that could appear with the results. Only those ads whose quality exceeds a certain preset threshold get placed in the mainline positions.” These ads are the most visible on the page and have the most effective positioning.

During the same two-month period, the search engine tweaked its ad-scoring algorithm so that the other half of the user group saw fewer mainline ads with their results. “The experiment increased the threshold cutoff of that algorithm just enough so that 17% of the ads that would have received mainline positions got pushed to less visible positions on the side of the page,” Sahni explains. Read the rest here.