WPP PLC, the world's largest advertising company, saw its stock plummet around 17.61% in the pre-market trading session on Thursday. This sharp decline came after the company reported a steeper-than-expected drop in its fourth-quarter revenue and issued a disappointing outlook for 2025.

In the fourth quarter, WPP's revenue less pass-through costs declined by 2.3% on a like-for-like basis, missing analysts' expectations of a 0.2% decline. The company faced challenges in key markets like North America and China due to account losses and economic pressures.

Adding to the investor concerns, WPP projected that its like-for-like revenue less pass-through costs would range from flat to a 2% decline in 2025, falling short of analysts' forecasts of a 1.8% rise. The weak guidance reflects the ongoing headwinds faced by the advertising industry, including the rise of generative AI and the growing dominance of tech giants in the market.