This pair of WSJ charts I like very much.
The article talks about the effect of early voting during Presidential elections in the States. People are allowed to mail in their votes as early as 2 months before the November 6 election.
The chart on the right identifies all the states that allow early voting, and in particular, it highlights (in orange) the seven battleground states that allow early voting. This shows the designer keenly aware of what's important and what's not important on the chart. The states are ordered by the first date of voting, instead of alphabetically. (I do have a question about why several of the gray lines towards the bottom of the chart do not reach November 6. Probably because mail-in voting is closed prior to Election Day in some states...)
If the data were to be available, a nice addition to this chart is to include the distribution of early votes over time. It's useful to see if North Carolina voters tend to spread their mail-in votes evenly over the 2 month period, or if most of them get sent close to Election Day, or some other pattern. Changing the bar chart to a dot plot and using the density of dots to indicate frequency would work fine here.
Instead of the first date of voting, the chart would be more informative if it plots the average date of voting (among mail-in voters). This is because the first date of voting is an extreme value and there may be few voters who vote on that day. If we have to pick one number to represent all early voters, we should pick the one with the average (or median) voting time. Again, this is constrained by whether such data is publicly released.
The chart on the left is also well executed. The title should include the additional fact that only battleground states are depicted. I'd also extend the vertical axis to 100% since the data are proportions. The beauty of this presentation is that it functions on several levels, whether you are interested in knowing that not much changed in Iowa from 2004 to 2008, or the fact that almost 8 of 10 mail-in votes in Colorado were early votes, or that in both Colorado and North Carolina, the proportion of mail-in votes more than doubled between 2004 and 2008.
Neither of these are fancy charts, but they pack quite a bit of useful information.
Please comment on the article here: Junk Charts