Rapidly increasing internet advertising spend is set to drive 4.7 per cent growth in total global ad spend this year, according to the latest forecasts from Zenith. Previously, ad spend had been tipped for four per cent growth this year, but internet ad investment has been exceeding expectations as of late.

Zenith estimates that internet ad spend grew 16 per cent last year – above the company’s forecast of 12 per cent. This means that the estimated total internet ad spend in 2018 has gone from $231n to $246bn.

Looking ahead, an average growth of 10 per cent a year for the next three years is now expected, leading internet advertising to reach $329bn and account for 49 per cent of global ad spend in 2021.

The main driving factors in the growth in internet spend are online video and social media, where growth of 19 per cent and 14 per cent a year to 2021 are expected respectively. Display advertising as a whole is expected to grow 13 per cent a year, with paid search and classified averaging at seven per cent growth each year.

“Internet advertising will exceed a quarter of a trillion dollars for the first time this year,” said Jonathan Barnard, head of forecasting and director of global intelligence at Zenith. “The speed of internet adspend growth continues to surprise us, as small businesses and digital challengers provoke established brands to up their game.”