Facebook Inc. produced big results for retail marketers in the second quarter, according to social media advertising firm Nanigans.

The vendor, which released a report examining 20 of the highest-spending e-commerce and game advertisers that used its platform over the past year, says the average return on its clients’ Facebook ad spend grew 75% in the second quarter. Those strong gains help explain why Nanigans’ advertisers boosted their Facebook ad spend 200% in the second quarter.

The vast majority of those ad dollars, 80%, are devoted to reaching consumers on mobile devices across all advertisers. However, the divide among desktop and mobile ad spending was far less extreme among online retailers; 65% of online merchants’ ad spending was allocated to mobile ads, a five percentage point jump from the first quarter and a 13 percentage point increase compared to the previous year.

One format retailers are using as they boost their spend is with the social network’s dynamic ads, which let retailers and other advertisers serve shoppers ads based on the products they looked at on the merchant’s site or app. Online retailers boosted their dynamic ad spending 14% compared to the first quarter.

The average click-through rate for Facebook ads for Nanigans’ retailer clients stood at 1.27% in the second quarter of 2016, up from 0.87% in the same period a year earlier. And the cost-per-thousand (CPM) impressions for the ads increased 91.9% to $6.37 in the second quarter compared with $3.32 a year earlier. The average cost per click grew to 50 cents in the third quarter, up 31.6% from 38 cents a year earlier.