Despite a recent rally, rising more than 37% over the last three months, a team of analysts at Morgan Stanley are expecting Twitter Inc.’s (TWTR) share price to plummet 50%, as the social media company battles with Facebook Inc. (FB) for advertising revenue. The team’s lead analyst, Brian Nowak, cited lack of change in advertisers’ intentions to spend and the risk of negative earnings revisions as factors that will weigh on the stock’s price in the near term, according to CNBC.

Battle for Ad Revenue

Twitter, which has yet to turn a profit, earns the majority of its revenue from advertising. Last year, advertising services comprised about 89% of its $2.53 billion total revenue. Advertising revenue is just as, if not more, important for Facebook, with advertising services bringing in over 97% of its $27.64 billion total revenue in 2016.

What is worrying for Twitter is that despite closing out its IPO year in 2013 with 120% growth in ad revenue, that growth has steadily declined to a mere 12.7% for all of last year. Meanwhile, Facebook has kept its ad revenue relatively steady over the same time period with growth accelerating from 48.6% during 2015 to 57.4% by the end of 2016. (To read more, see: Facebook Is Putting Ads … Everywhere.)

Back in the spring, one head of a social media firm revealed to Ralph Schackart at William Blair, a financial services company, that her firm was planning to increase ad spending on social media by about 20% year over year with spending on Facebook advertising to increase by around 35% while spending on Twitter would decrease between 20% and 30%. If this example is any indication, Facebook will likely continue to see strong ad revenue growth while Twitter’s will falter.

Twitter’s Travails

One of Twitter’s biggest challenges in competing with social media giants like Facebook is its size. Big advertisers want to reach as many consumers as possible, and with Facebook’s roughly 2 billion monthly users dwarfing Twitter’s 328 million, according to Tech Crunch, it’s not hard to see which platform offers the bigger exposure.

On the positive side, Twitter reported better than expected user growth for the first quarter of this year, which caused its stock price to shoot up at the end of April sparking the three-month rally.

Yet, Twitter’s attractiveness to advertisers pales in comparison to Facebook when it comes to its targeting capabilities. As a much more dynamic social media platform, Facebook has access to greater amounts of diversified data, allowing it to create more complete personality profiles of its users. This ability allows for much more targeted advertising. (For more, see: Capitalizing on Mobile Advertising: Twitter Vs. Facebook Vs. Google.)

While Facebook appears to be winning the battle for ad revenue, CNBC did note that despite the negative forecast from Nowak’s team, one boutique equity research firm, Cleveland Research, claimed near the end of June that advertisers’ opinions of Twitter had reached its most optimistic in over two years.

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