SimilarWeb puts together a monthly ranking of the largest U.S. media companies and publishers, and the latest one has MSN at the top with almost 2 billion desktop and mobile page-views. But the chart also measures what SimilarWeb says are the total number of Facebook visits to a publisher’s sites.

According to those numbers, some of the largest news publishers on the web have seen significant declines in traffic from the giant social network. Among the biggest losers are Newsweek owner IBT Media, which saw its visits drop by 47% in the second quarter, and TheStreet.com, which saw a drop of 53%.

The Gannett newspaper chain’s traffic from Facebook fell by 26%, according to SimilarWeb’s ranking, while the New York Times fell by 25%. Time Inc. (which owns Fortune) saw Facebook visits fall by 25%, Vox dropped by 35% and German giant Axel Springer—which owns Business Insider—saw a drop of 28%.

In terms of traffic to individual websites, which SimilarWeb also measures, some also saw sharp declines from the beginning of the year. CNN’s Facebook visits from Facebook were down by 33%, the Washington Post‘s traffic was off by 26% and Politico saw a drop of 38%.

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A number of publishing-industry insiders disputed the SimilarWeb figures, but other analytics and measurement services have also described declines in Facebook traffic over the past few months, likely as a result of a number of changes to the site’s ranking algorithms.

In one change earlier this year, Facebook (FB) said that it was going to de-emphasize articles from mainstream media sites in favor of posts from a user’s friends and family. Any decline in Facebook traffic can have a huge impact on media companies because they rely on that traffic for a large proportion of their advertising revenue.

BuzzFeed publisher Dao Nguyen pointed out that the SimilarWeb numbers only apply to desktop visits from Facebook, which suggests that some of the decline could be a result of web traffic moving to mobile. About half of the social network’s 1.4 billion users access the site primarily on a mobile device.

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Social analytics firm SocialFlow said recently that the “reach” of a particular post on Facebook—meaning the total number of users who see it—has fallen for some publishers by as much as 52% from January through July.

However, the company noted that this could be because media companies are producing more and more content, and therefore the reach of any given post is going to be lower.