If you have not seen Spotlight (2015), the film about The Boston Globe's investigation into institutional silence over child abuse, then you should watch it right now. More to the point—you should watch right through to the title cards at the end.

A list scrolls down the screen. It details the dozens and dozens of places where abuse scandals have been uncovered since the events of the film, from Akute, Nigeria, to Wollongong, Australia. But the title cards also cause us to pause in our celebrations: One of the key figures involved in the scandal, it says, was reassigned to “one of the highest ranking Roman Catholic churches in the world.”

This is the challenge of impact in data journalism: Is raising awareness of a problem “impact”? Does the story have to result in penalty or reward? Visible policy change? How important is impact? And to whom?

These last two questions are worth tackling first. Traditionally, impact has been important for two main reasons: Commercial and cultural. Commercially, measures of impact such as brand awareness and high audience figures can contribute directly to a publication's profit margin through advertising (increasing both price and volume) and subscription/copy sales (Rusbridger, 2018). Culturally, however, stories with impact have also given news organizations and individual journalists “bragging rights” among their peers. Both, as we shall see, have become more complicated.

Measurements of impact in journalism have, historically, been limited: Aggregate sales and audience figures, a limited pool of industry prizes, and the occasional audience survey were all that publishers could draw on. Now, of course, the challenge lies not only in a proliferation of metrics, but in a proliferation of business models, too, with the expansion of non-profit news provision in particular leading to an increasing emphasis on impact and discussion about how that might be measured (Schlemmer, 2016). Furthermore, the ability to measure impact on a story-by-story basis has meant it is no longer editors who are held responsible for audience impact, but journalists, too.