Facebook Inc.’s ads delivered results for retail marketers in the crucial fourth 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 33% in the fourth quarter. That was helped in part by e-commerce purchase rates growing 68%.

Retailers’ ad dollars continued their shift to mobile ads from desktops during the quarter, the vendor says, noting that mobile e-commerce ad spending rose 23%. Mobile video ads accounted for some of that growth, accounting  for 18.9% of mobile ad spending in the Americas, roughly a 20% jump from the third quarter.

However, the most significant growth came 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 164% year over year.

The average click-through rate for Facebook ads for Nanigans’ retailer clients stood at 1.77% in the fourth quarter of 2016, up from 1.06% in the same period a year earlier. The average cost per click fell 40.6% to 41 cents in the fourth quarter compared with 69 cents a year earlier. And the average cost-per-thousand (CPM) impressions fell 1.5% to $7.24 from $7.35 a year earlier.

The Nanigans report comes on the heels of the release of Hitwise data that showed that social networks’ ads accounted for 3.6% of traffic to retailers’ sites over the holidays, roughly 10 times the 0.25% share they generated in 2015.