The uptick in social media spending is part of broader growth in the ad industry. Global advertising expenditure will grow 4.4 percent in 2017, matching the same pace seen in 2016, despite political uncertainties such as the U.S. presidential election and the U.K.'s referendum on European Union membership, according to the report.
Zenith forecasts ad spend to growth 4.4 percent in 2018 and 4.1 percent in 2019.
"Global adspend growth has been remarkably stable since 2010, growing at between 4 percent and 5 percent a year, generally at or below the growth rate of global GDP (gross domestic product). Before the financial crisis, advertising would typically exaggerate the wider economy, growing faster in times of expansion and shrinking faster during recessions, with frequent changes in year-on-year growth rates. More recently the global ad market appears to have entered a phase of more stable growth," the report said.