Morgan Stanley analyst Brian Nowak said he remains bullish on Amazon’s ad opportunity and he raised his 2018 and 2019 ad revenue estimates by 5% and 12%, respectively.

After talks with members of the industry and ad agencies, he found that most of Amazon’s ad dollars are coming from traditional branded trade spend, including vendor allowances.

Nowak estimates there is currently $55 billion spent in the U.S. on vendor allowances, which he identifies as the most natural new source of dollars for online advertising leaders Amazon, Google Shopping (GOOG) and Facebook (FB) as brands fight for visibility and “online shelf space,” he tells investors. The analyst raised his price target on Amazon shares to $1,400 from $1,250 and increased his “bull case” value to $2,100 from $2,000.

Nowak keeps an Overweight rating on Amazon shares.