You can find a lot of bad data graphics about Covid-19. (Remember those outright deceptive charts from Georgia’s Department of Public Health?) Fortunately, the Canadian Broadcasting Corporation has made some very good ones.
For 18 months the CBC’s Vancouver bureau published daily charts to illuminate British Columbia’s fight against Covid. Justin McElroy, the charts’ creator, has probably never heard of The Golden Rule of Charts and Graphs: “Display all the information you need to tell an honest story, and no more.” But he applied these principles to his data graphics.
Let’s examine how the chart above puts the golden rule to good use:
1. Tell a story. This chart’s headline doesn’t broadcast its story, but the data makes that story clear: Covid deaths in BC rose sharply in late 2020; after Canada began vaccinations, deaths fell.
2. Display all the information you need, and no more. The chart contains everything readers need to understand the data, but doesn’t overwhelm them with information.
The CBC starts with the basics: Who provided the data (BC Centre for Disease Control) and who made the chart (Justin McElroy, CBC News). The axes are well-labeled. The chart contains two data lines: one precise-but-noisy number (new deaths reported each day) and one less-detailed number that shows trends more clearly (rolling seven-day average). The time periods before and after Canada began vaccinations are distinctly labeled.
Labeling each of the 1,000 data points would make this chart unreadable. But McElroy added a feature to help readers who want more detail: Mousing over any point on the chart displays the exact date and data point.
Covid-19 line chart highlighting a specific data point for May 12, 2021. Image source: CBC.
3. Make sure it’s honest. The CBC’s chart presents the government’s data simply and directly. McElroy didn’t manipulate either axis or scale. He even anticipated readers’ confusion over a data point showing negative three Covid deaths on May 5, 2021, and noted this was due to a government data correction.
It’s not hard to make a good data graphic. Unfortunately, it’s a lot easier to make a bad one. I appreciate Justin McElroy and the CBC BC making effective Covid tracking charts and helping people better understand the pandemic.
What’s the best or worst Covid data graphic you’ve seen? Let me know in the comments below, or on LinkedIn or Twitter.
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