Snapchat is set to make £68.4 million ($88.1 million) in U.K. ad revenues this year, down from a projected £104.8 million.
Figures from eMarketer show that while Snapchat's ad revenues will increase to around £136 million in 2020, its share of companies' digital ad spend will grow slowly.
Currently, Snapchat takes 0.5 percent of the digital advertising market in the U.K., which is up from 0.3 percent in 2017, but below a predicted 0.8 percent. Google, meanwhile, takes 39.1 percent of digital ad spend in the U.K., with Facebook controlling 21.7 percent.
One of the reasons Snapchat's ad revenues are set to grow more slowly is its transition to an automated, or programmatic, ad system. It launched this self-service ad platform in June 2017 — while this has increased the number of advertisers, the cost of ads has reduced, according to eMarketer's Principal Analyst Debra Aho Williamson.
"Programmatic ads are typically cheaper because the automated auction infrastructure reduces (and sometimes eliminates) the need for salespeople to get involved," Williamson said in an emailed statement.