Twitter, compared to Facebook, Google, and even Yahoo, really isn’t very good for driving referral traffic. This is at least the case when it comes to news publishers as new data from Parse.ly finds.

This week, Nieman Lab shared data from the company, which looked at 200 of its client websites. These include Upworthy, Slate, The Daily Beast, and Business Insider. While Twitter’s value for breaking news is certainly acknowledged, it concludes that Twitter is a small source of traffic for most publishers with less than 5% of referrals coming from Twitter in January and February.

The following chart illustrates how Facebook and Google completely dominate referrals compared to everything else. It’s not as if Twitter is the only small piece of the pie here. It’s just that you might expect it to be bigger considering its place in the media. It certainly doesn’t help that the company continues to struggle to grow its user base.

Of course there are exceptions. Some publishers are able to squeeze more out of Twitter than their peers. In fact, Nieman Lab says about 15% of its traffic comes from Twitter, pointing to its “digitally savvy journalists” audience.

The very nature of the Twitter timeline is likely a major obstacle for referral traffic though. It’s often a case of information overload and excessive noise. Twitter’s recently introduced algorithmic timeline changes could help in that department for those that manage to cut through. This only became the default in March (after the Parse.ly data was recorded).

Twitter made another recent change that will only make it harder to track referrals though. Earlier this month, Twitter announced the launch of a new message button it actually pre-announced two years ago. The button appears on tweets to let users share the tweet via direct message.

“Every day, millions of people send Direct Messages to communicate privately with friends, family, experts, brands, and anyone else they find interesting on Twitter,” says product manager Somas Thyagaraja. “In fact, we’ve seen the number of messages sent grow over 60% in 2015. And the number of Tweets shared privately has grown even faster, at 200% in just the second half of last year.”

“With all this interest, we’ve also heard from many of you that it could be easier to share a Tweet using Direct Message,” adds Thyagaraja. “So now — in just a few taps — you can share unique Twitter content from your timeline right into your private conversation.”

According to Patricio Robles at Econsultancy, referrals from these private tweets will fall under “dark social,” meaning you’ll not be able to track their source. Dark social traffic shows up as “direct” in analytics tools like Google Analytics. Simply Measured has a great explainer on this here.

Image via Parse.ly/Nieman Lab