Two sources are not always two sources

Why DeepInquiry groups sources by website and parent company before it counts them.

Most fact checks rest on a simple rule: a claim is verified when two independent sources agree. The rule is sound. The difficulty is that almost nobody defines what “independent” means, and the web makes the difference hard to see.

Consider the ways that two sources can turn out to be one.

• A shared owner. The Wall Street Journal, MarketWatch and Barron’s are all owned by News Corp. A claim that appears in all three has been published by one company, three times.
• A copied page. Wikipedia has many mirrors, and aggregators republish government and vendor data. Citing the copy is citing the original, one step removed.
• A wire story. A single Associated Press or Reuters report can appear on hundreds of websites. The websites differ; the reporting does not.
• A circular claim. In a well-documented case, a false edit to a Wikipedia biography was repeated by several news outlets, which were later cited as support for the edit. Wikipedia keeps a list of such incidents.

DeepInquiry handles the first two before it counts anything. Each candidate source is grouped by website, and by parent company for the websites we have mapped, so outlets under one mapped owner count once. Wikipedia, its mirrors and aggregators are set aside whenever a source of another kind exists. The count that remains is a count of source groups rather than links.

Every fact in the library has its own page listing its sources, and the API returns a gold, silver or bronze tier for each fact together with the groups behind it. The library currently holds 2,806 published facts. One example is the wood frog that survives being frozen solid, where the page lists the sources so that a reader can check them.

What the grouping does not do. It does not detect wire reprints, copied wording, or several outlets reporting one study. We say so on our methodology page, because a number that overstates what it measures is worse than no number.

If you build with facts, whether in a product, a research tool or an AI system that needs citations, the API is free to try at 500 requests a month. Documentation is at deepinquiry.ai/docs.