Zenith, owned by French advertising group Publicis, said advertisers will make more effective use of personalised messages as online video advertising grows by an 18 percent a year between 2018 and 2021.

That growth rate is twice as fast as other forms of online display advertising and well ahead of any other channel, Zenith said, adding that e-commerce advertising is expected to add about $100 billion (78 billion pounds) of new money into the global advertising market.

Businesses are taking advantage of the new digital opportunities available to them, said Vittorio Bonori, Zenith's global brand president.

"Better segmentation and targeting, personalised creative and direct transactional relationships with consumers are combining to drive brand growth," he said.

In terms of overall advertising spending growth, India will be the stand-out market, with Zenith forecasting growth of 13.5 percent a year from $9.7 billion in 2018 to $14.2 billion in 2021. That would make India the world's eighth-largest advertising market, entering the top 10 for the first time.

(This story corrects an earlier version to remove extraneous word 'embargoed' in headline)

(Reporting by Sangameswaran S in Bengaluru; Editing by David Goodman)