I generally love Mike Bostock's work, and this is a beautiful visualization, but I think this comment points out why circles are just a bad way to represent anything visual other than pizzas: it's a leaky abstraction (which is a real sin in visualization)
You have to know how the chart is generated in order to correctly interpret what you're seeing. The value can be the radius, diameter (how pizzas are measured) or the area itself! All of these choices lead to different interpretations of what you're seeing.
Then, on top of that, we're just not great and visually comparing areas. Pizzas are a great example of this. A 12" pie and a 16" pie don't look that different but you're talking about nearly twice the amount of pizza! A good example in this visualization is Signature vs SVB
Then on top of that we have the dimensions of the circle forcing the visual to overlap on the x-axis without this meaning anything concrete.
All that you can meaningfully take away from this visually is "2008 had one big and a ton of small failures, and currently we're seeing 3 big, but not quite as big failures", and unfortunately there's not a lot more you can get out of this. Because of the x-axis problem it's hard to even tell if WaMu preceded some of the others or not.
You have to know how the chart is generated in order to correctly interpret what you're seeing. The value can be the radius, diameter (how pizzas are measured) or the area itself! All of these choices lead to different interpretations of what you're seeing.
Then, on top of that, we're just not great and visually comparing areas. Pizzas are a great example of this. A 12" pie and a 16" pie don't look that different but you're talking about nearly twice the amount of pizza! A good example in this visualization is Signature vs SVB
Then on top of that we have the dimensions of the circle forcing the visual to overlap on the x-axis without this meaning anything concrete.
All that you can meaningfully take away from this visually is "2008 had one big and a ton of small failures, and currently we're seeing 3 big, but not quite as big failures", and unfortunately there's not a lot more you can get out of this. Because of the x-axis problem it's hard to even tell if WaMu preceded some of the others or not.