If you’re reading this handbook, you’ve decided that you want to learn a little about the trade that's become known as data journalism. But what, exactly, does that mean in an age of open data portals, dazzling visualizations and freedom of information battles around the world?

A dictionary definition of the two words doesn't help much—put together, it suggests that data journalism is an occupation of producing news made up of facts or information. Data journalism has come to mean virtually any act of journalism that touches electronically held records and statistics—in other words, virtually all of journalism.

That's why a lot of the people in the field don't think of themselves as data journalists—they’re more likely to consider themselves explanatory writers, graphic or visual journalists, reporters, audience analysts, or news application developers—all more precise names for the many tribes of this growing field. That's not enough, so add in anything in a newsroom that requires the use of numbers, or anything that requires computer programming. What was once a garage band has now grown big enough to make up an orchestra.

Data journalism is not very new. In fact, if you think of “data” as some sort of systematic collection, then some of the earliest data journalism in the United States dates back to the mid-1800s, when Frank Leslie, publisher of Frank Leslie's Illustrated Newspaper, hired detectives to follow dairy carts around New York City to document mislabelled and contaminated milk. Scott Klein (2016), a managing editor for the non-profit investigative site ProPublica, has documented a fascinating history of data journalism also dating to the 1800s, in which newspapers taught readers how to understand a bar chart.