Fact-checking sites have emerged as "a new democratic institution" in many European countries, according to a report published Tuesday by the Reuters Institute for the Study of Journalism.

Since the first regular source of political fact-checking started publishing in Europe in the mid-2000s, fact-checking initiatives have launched across much of the continent, the authors found.

Today at least 34 permanent sources of political fact-checking are active in 20 different European countries, from Ireland to Turkey. They can be found on every part of the continent, including the Nordic countries, the Mediterranean, Central Europe, the Balkans, and the former Soviet republics. In addition, fact-checking as a genre is sufficiently well established that many news outlets without dedicated teams offer it on an ad hoc basis, for instance during major political campaigns.

Even though independent political fact-checking is a relatively recent phenomenon, several initiatives have already shut down:

More than 50 dedicated fact-checking outlets have launched across Europe over the past decade, though roughly a third of those have closed their doors or operate only occasionally.

This work isn't solely, or even primarily, conducted by traditional media outlets. The report analyzes extensively what it calls the "NGO model" of fact-checking.

Many European fact-checking outlets are attached to established news organizations, like Channel 4 News. But a majority — more than 60 percent in the companion survey conducted for this report — are not, operating either as independent ventures or as projects of a civil society organization.

With the role of political fact-checking in American journalism the object of increased scrutiny, the authors note that non-journalistic fact-checkers in Europe see the traditional media as both a partner and a rival.

As a democratic institution the practice raises basic questions about what counts as reliable data, who has the authority to assess public truth, and how to balance accuracy with other democratic ideals such as openness and pluralism. It represents a clear challenge to legacy news outlets in Europe, whom fact-checkers depend on to publicise their work but in many cases see as an institution in dire need of change.

Funding across many of these projects is, if not shaky, dangerously dependent on a single source.

Fact-checking across Europe depends above all on two financial anchors, the media industry and charitable foundations. In our survey, one-third of responding organizations relied on a media parent as a major funding source — typically the only one.

The report was written by Federica Cherubini, now head of knowledge sharing at Condé Nast International, and Lucas Graves, a University of Wisconsin professor of journalism and author of "Deciding What's True: The Rise of Political Fact-Checking in American Journalism."

Disclosure: I was interviewed by the authors of this report to discuss my previous work at the Italian fact-checking site Pagella Politica and to offer my perspective on fact-checking in Europe overall.