Another characteristic was the fact that the maps were all interactive. Seeing data is one thing, but to be able to manipulate it and have it highlight or isolate information, provides a more fun experience when dealing with numbers is often...boring. Studies that only show a two-dimensional illustration of data, or just show charts and numbers, lack that extra oomph to draw readers in to want to really understand how these numbers play out in their everyday lives.
Finally, the third attribute of these data visualization articles is that they offer some continuity among other articles published by the New York Times. As most articles do, there was a "Related articles" link- but for this, it offers more depth into the same topic presented by the data- some even using the same data within the article. For example, "The Changing Nature of Middle- Class Jobs" had a related article titled "Middle Class, but Feeling Economically Insecure" which ultimately takes the numbers presented in the data and translates that into how people are actually living, thinking and feeling.
Ultimately, all of these articles present a lot of information in a way that is more digestible and easier to consume. By creating a visual that breaks down the information and provides greater context, it allows readers to better understand how these numbers tell a much bigger story.