“P.L.A.s takes the search engine results page to a different level,” said Andy Taylor, Merkle’s associate director of research.

A Google spokeswoman said the company’s goal had always been to quickly give people the best search results.

“Our goal has always been to deliver results that people find immediately useful, which is even more important on mobile devices with smaller screens,” said the spokeswoman, Chi Hea Cho. “For most queries, we show no ads, and we recently removed right-hand text ads for all queries. For highly commercial queries, our extensive testing shows that people find relevant ads and offers extremely useful.”

The importance of being at the top of search results is fueling fierce competition for ads. Reef, a beachwear manufacturer best known for its sandals, said it increased spending with Google by 76 percent last year — mainly because it nearly quadrupled the money it put into product ads.

On a search result, Reef is competing with other manufacturers of flip-flops, as well as retail partners selling Reef sandals. On a desktop computer, a Google search for “Reef flip-flops” brought back three text ads above the search results — one from Reef, one from Zappos and one from Amazon — selling Reef sandals. There were also nine image-based product listing ads displaying different Reef sandals for sale; only three were offered by reef.com while the rest were ads from other retailers.

On a mobile phone, Reef is competing with even more retailers. The same search brought back only Reef’s text ad, but below a scrolling carousel featuring more than 20 image ads for different types of Reef flip-flops. Only the first two images linked to reef.com.

“We’re competing against each other,” Jessica Levens, director of e-commerce at Reef, said about the company’s retail partners. “We need to spend the dollars to defend that real estate.”