Global ad giant WPP reported lower-than-expected full-year revenue, sending its share price tumbling up to 18%, as it struggles to keep pace with rivals amid cost-cutting in the adtech industry.

The company behind VML and Ogilvy saw revenues fall nearly 1% from £14.85 billion to £14.74 billion in 2024, while operating profit was up 2%.

CEO Mark Read noted that the revenue slip was partly due to “weaker client discretionary spend” towards the end of the year. The London-based company also saw softer demand for its services from North America and China.

For 2025, WPP expects organic revenue to be anywhere from flat to down 2%.

"Given the newsflow, particularly from the U.S., there are many reasons that we are cautious about the year," Read said. "The new administration wants to get America growing strongly, but there's no doubt that tariffs and subsequent inflation is making people nervous."

WPP shares were down 15% as of 11:30 a.m. London time, making it the biggest loser in the FTSE 100 index.

WPP is grappling with changes in the advertising sector and within the organization.

At the start of 2024, the Fortune 500 Europe-listed company set out to restructure its brands and slash costs by merging agencies, shedding others, and simplifying its media investment unit, GroupM. Read also aimed to make AI front-and-center at the time . Read said the company made good progress on these efforts throughout the year.

Still, the ad company slipped behind competitors last year, including France’s Publicis and the U.S.-based Omnicom. WPP has also had to defend itself against squeezed budgets at tech companies and beyond.

Read has flirted with the idea of getting “closer” to the U.S. in the hopes of driving topline growth that would lift WPP’s share price.

While WPP is under pressure to regain share from its rivals, it rolled out a sweeping RTO mandate in January, calling most of its 114,000 workforce back to work at least four times a week.

In a memo sent to employees, Read said that staff could turn to “an AI-powered chat agent” to answer any questions about the new RTO rule that would kick in in April.

Today, Read reiterated his belief in a return to office being in the company's best interests, telling analysts on a call that “as you know at WPP, we believe in-person working is better in the long run for the organization than remote working.”

Following the original announcement, a spokesperson at WPP told Fortune that the new mandate would apply to everyone, regardless of which agency within WPP they belonged to. It would exclude those with existing remote work contracts in place.