When advertisers launch new digital campaigns, it is almost guaranteed that they will call upon either Facebook (FB) or Google (GOOG).

According to analysis of the Interactive Advertising Bureau’s (IAB) latest report by Pivotal Research senior analyst Brian Wieser, the two tech giants were responsible for an incredible 99 percent of revenue growth in the mushrooming market last year. Wieser included his finding in a note to clients seen by Business Insider.

Wieser claimed that Facebook and Google’s duopoly​ of digital advertising is so strong that they captured a combined 77 percent of gross spending in 2016 — a 5 percentage point increase on 2015. Facebook, he added, had a particularly strong year, accounting for 77 percent of the market’s overall growth. (See also: Facebook, Google Thrive as Digital Ads Hit Record.)

Mobile Advertising Spend Surges

IAB's latest report revealed that U.S. companies spent a record-breaking $72.5 billion on advertising last year. Driving this 22 percent increase was a surge in mobile advertising expenditure, which, at $36.6 billion, accounted for just over half of the total figure. (See also: Alibaba May Earn $16B In Mobile Ad Revenue in 2017.)

“Mobile fueled the internet economy in 2016, with advertisers showing their confidence in digital to achieve their marketing goals,” said Randall Rothenberg, president and CEO of IAB. “This increasing commitment is a reflection of brands’ ongoing marketing shift from ‘mobile-first’ to ‘mobile-only’ in order to keep pace with today’s on-the-go consumers.”

Source: IAB

According to the report, videos remained one of the most popular channels for marketing campaigns. Digital video revenues hit a record $9.1 billion in 2016, up 53 percent year-over-year, while videos on mobile devices surged 145 percent year-over-year to nearly $4.2 billion.

Elsewhere, social media advertising sales climbed 50 percent to $16.3 billion, while search revenues rose 19 percent to reach nearly $35 billion. Digital audio, which was measured for the first time in the report, generated $1.1 billion of sales.

David Silverman, a partner at PwC U.S, the professional services network that was responsible for preparing the report, claims the latter data shows just how much the advertising market is changing. “Digital audio, generating $1.1 billion in 2016 speaks to the continued evolution of new formats that enable marketers to find audiences at home, behind their desks, or wherever they are,” he said.​

Want to learn how to invest?

Get a free 10 week email series that will teach you how to start investing.

Delivered twice a week, straight to your inbox.