If these events were neutralised, growth in 2018 would fall to 4.1%, Magna said, which is closer to Group M's prediction today of 4.3%.
"The classic quadrennial drivers (FIFA World Cup, Winter Olympics and US Elections) will offset the underlying slowdown of the global advertising market in 2018 to generate decent growth," Vincent Létang, executive vice-president, Global Market Intelligence at Magna and author of the report, said.
However, Magna, which is run by IPG Mediabrands, is far less rosy on the UK predicting the ad market will only grow 2.3% in 2018 - far less positive than Group M's forecast of 4.8%.
In the US, Magna expects advertising sales to grow by 5% in 2018 to reach $195bn thanks to the cyclical events mentioned above. If these events were to be neutralised, 2018 growth would only be 3.2% compared with 3.9% in 2017.
Overall, 2018 will be a largely positive one for the world. Out of 70 markets analysed by Magna, only one, Singapore, is expected to shrink.
Within the top 20 markets, the highest growth rates are expected from India (12%) and Russia (10%). China also remains robust (9%) despite some vertical spending (such as automotive) slowing down.
Digital and mobile
Globally, digital and mobile advertising sales will grow by 13% in 2018 to reach $237bn or 44% of global advertising revenues. Magna expects that they will comprise half of all ad sales by 2020.
Digital advertising sales surpassed TV in 2017, as previously forecast, reaching a 41% market share (compared to 35% for linear television). For 2018, Magna anticiaptes that digital media sales will reach 44% of total ad sales in 2018.
Within digital, the majority of advertising sales (55%) is now generated by impressions and clicks on mobile devices.
Mobile ad sales grew by 39% in 2017 and will grow again by 27% in 2018 to reach 62% of all digital ad sales.
Search and social formats continue to drive digital advertising growth (growing by 16% and 40%, respectively, in 2017) as billions of below-the-line, direct marketing dollars are being redirected towards these formats.
Social and search now represent 70% of digital media spend, compared with 24% for display banners and video.
Linear TV adspend is expected to grow in 2018 by 2.5% to $183bn thanks to the return of the cyclical events. Without the incremental even-year ad sales, TV would be flat next year (-0.1%).
The multi-year normalised growth for TV is thus slowing down gradually, from 0.8% in 2016 and 0.6% in 2017 as viewing erosion accelerates and digital alternatives are increasingly available to advertisers.
Out-of-home will be the only other offline media channel to grow in 2018. It is expected to grow 3% to $33bn.
Print ad sales, however, will drop by 11% to $54bn and radio ad revenues will shrink by 2% to $28bn.
"The transition to a digital-centric media world accelerates as digital ad sales continue to grow as fast - and often faster - than expected," Létang said. "Meanwhile, linear television struggles in most major markets (US, UK, Australia and so on) as CPM inflation is no longer strong enough to compensate for declining ratings and lower demand from consumer goods."