• Amazon is set to bring in $4.61 billion from digital advertising this year, according to a new estimate from eMarketer.

• That only represents 4.1% of U.S. digital ad spending.

• In surpassing Oath and Microsoft, Amazon is now the front-runner to challenge Facebook and Google.

Amazon will surpass Oath and Microsoft to become the third largest digital ad seller in the U.S. behind Facebook and Google. That’s the latest from research firm eMarketer, which predicts Amazon’s ad growth will more than double this year.

As eMarketer notes, the change in projection — up 60 percent from March — is due to a combination of an accounting change and 10 to 12 percent increase in stronger-than-expected ad revenue growth.

The firm expects Amazon ad revenue to increase by more than 50 percent per year through at least 2020. The duopoly’s share is pegged to shrink from 57.7 percent in 2018 to 55.9 percent in 2020 while Amazon’s share is expected to grow from 4.1 percent to 7.0 percent.

While Amazon has a long way to go to truly rival Google and Facebook’s ad earnings, its ad business is still relatively young with lots of runway ahead.  Earlier this month, Amazon announced it is making it easier for advertisers to buy ads on and off its properties. It’s introducing more video advertising formats and provides advertising options both on and off its owned and operated properties.

Related reading

• Analysts say Amazon’s advertising business will surpass AWS by 2021

• Amazon streamlines ad products under new Amazon Advertising brand

This article originally appeard on Marketing Land.