Light entertainment: a ribbon chart

A reader sent in this amusement. See if you can figure out the chart:

Motorbiker_chart

The article is here. It then goes into a lot of numbers about 200 accidents. I didn't pay much attention after that first paragraph, where it said 16% of the accidents were in one year, with 84% in the next year. That implied a growth of more than five times from one year to the next. Seems to me an issue with data collection. The author then goes on to aggregate the two years, and reports dozens of findings.

Anyway, what is the point of the ribbon chart?

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