Visualizing Election Polling Data: What to Know

We’re one week away and, as ever, all the media outlets have an election poll tracker. How do they stack up? Do they mislead? Do they adhere to good practice? Do they communicate well with their audience? What can we, as data analysts, learn from these?.

Today I’m taking a look at 5 trackers from across the media and political spectrum.

Overall, there’s lots to like. I didn’t find any egregious visualization crimes. Instead, I found simple charts, attempts to show uncertainty, and some new ways to tell stories. Take, for example, the Guardian, FT, and BBC trackers.

Each tracker has a couple of nice features the others’ don’t, as well as a couple of things I might like to see improved upon. Taking a deeper dive:

The Guardian

The front page of the Guardian’s election site doesn’t show the tracker. Instead it shows BANs: the headline numbers.

Do I like this? Well, I wrote the book that introduced BANs to the world, but here, I’m not so sure. Headline numbers are amazing, but in an election, it’s the value relative to the others and how it’s changing that is most important.

I think that for the front page real estate taken with these numbers, it would be possible to show the info with some sparklines. Something like this, perhaps:

With that approach, we get the headline numbers, but also the sense of change—as well as a way to compare parties visually and quickly. Sparklines are great for mobile, too, as they will shrink down really small while maintaining readability.

The Poll Tracker itself is the only one of the three with interactivity. Hover over a dot and it highlights all the polls by that pollster, for that political party:

I like this interactivity because it builds a deeper insight into each pollster.

Beneath the line chart is another interactive chart, showing all the polls, row by row. I like this too: it’s a visual representation of row-level detail (contrast that with the BBC and FT, which both have plain tabular data beneath their trackers).

The FT

The FT tracker lacks the interactivity of the Guardian, but is otherwise equally well done. There is one nice extra feature.

BBC

How does the BBC do it? As we’ve seen above, they have the same overall approach. The top of the BBC tracker has a headline section, too.

This is the only tracker to show the “Likely Range”. I think this is really important, because it’s the only one to show, in “headline” form, the uncertainty in the data. Including “Likely Range” lets us see how close the parties might be at the upper/lower ends of the ranges.

I have two small quibbles with the BBC’s tracking chart, which I call out on the chart below with red markers:

Number 1: Which line is this label referring too? I was confused. It’s a reference line label to the solid red line, not the dotted grey line. It took me a moment to work that out. I originally interpreted the solid red line as a border, not a reference line.

Number 2: The BBC chose to include more party lines than the FT and the Guardian, and the result is that the smaller parties’ lines become unreadable. Try following the black line from start to end: It gets lost.

Daily Mail

The Daily Mail doesn’t seem to have a tracker per se, but is publishing regular articles about polling data. I quite like that approach: it makes the polling numbers more of a news item than something to remember to go check in with.

There are a couple of things to like. They chose bar charts, which is great. There’s a nice clear headline. That tells me what I am looking at. But there are issues:

My own tracker: Tableau-built!

Finally, I thought I’d build my own tracker, using Tableau.

I took the data and combined the interactivity of the Guardian with the right-hand BANs of the FT. I didn’t push the needle out.

View the interactive version