Fake news evolved from seedy internet sideshow to serious electoral threat so quickly that behavioral scientists had little time to answer basic questions about it, like who was reading what, how much real news they also consumed and whether targeted fact-checking efforts ever hit a target.

Sure, surveys abound, asking people what they remember reading. But these are only as precise as the respondents’ shifty recollections and subject to a malleable definition of “fake.” The term “fake news” itself has evolved into an all-purpose smear, used by politicians and the president to deride journalism they don’t like.

But now the first hard data on fake-news consumption has arrived. Researchers last week posted an analysis of the browsing histories of thousands of adults during the run-up to the 2016 election — a real-time picture of who viewed which fake stories, and what real news those people were seeing at the same time.

The reach of fake news was wide indeed, the study found, yet also shallow. One in four Americans saw at least one false story, but even the most eager fake-news readers — deeply conservative supporters of President Trump — consumed far more of the real kind, from newspaper and network websites and other digital sources.