Performance-marketing agency Merkle on Thursday released its Q2 2018 Digital Marketing Report (DMR) analyzing trends across paid and organic search, social media and display. The data provides insights into trends across Amazon, Bing, Google, Instagram, Facebook and Yahoo.

Some of the most interesting findings point to Amazon search ads, which continue to grow in popularity.

Marketers spent more on Sponsored Products, up 165%, during the second quarter of 2018. This ad group continues to account for the majority of Amazon search investment, taking 88% spend share in Q2.

They also drive the highest sales per click for advertisers among Amazon’s search formats.

While Sponsored Products took the majority of ad spend in the quarter, the amount spent on Headline Search Ads also rose, up 162%, year over year (YoY).

Analyzing advertising bids on both formats, Sponsored Products and Headline Search Ads clicks convert at more than three times the rate of Google Shopping ad clicks, according to the report. The report also calls out many advertisers on Google Shopping that do not sell on Amazon and thus don’t bid on Amazon’s ad formats, while some Amazon sellers don’t sell through Google Shopping.

It’s also important to note the CTR for Amazon Sponsored Products comes out to less than half that of Google Shopping. Merkle attributes it largely to the presence of Headline Search Ads at the top of Amazon search results which Sponsored Products also serves up.

Google Shopping ads compete with text ads for clicks, but they typically serve above text ads when both formats appear. Headline Search Ads CTR was 42% higher than Google Shopping in the second quarter of 2018.

Spending on Google Shopping ads rose 31% in the quarter, more than five times the rate of growth for Google text ads. While Google text ad spending growth improved by 6%, up from 4%, sequentially, the rate remains well below levels seen throughout 2017.

Impression growth for Shopping Ads has been healthy, likely cannibalizing impressions for text ads, according to the data.

It is clear from Merkle’s numbers that marketers are spending more on mobile. Spending on desktop Google search ads plummeted in the second quarter. Desktop grew a mere 12% YoY, its lowest rate of growth since the third quarter in 2016.

Search ads for mobile on Google rose 37% YoY in the quarter. Tablet spending declined 2%, up from an 11% decline a quarter earlier.