Because there are so many Jettas in the system, there have to be at least two vehicles to show a particular fuel economy on the graph. So unless two Jettas have 59 MPG, that fuel economy number won't appear on that graph. Some vehicles have far fewer in the system, so a single fuel economy can make it onto the graph.
This particular graph is all about showing the average fuel economy, not the outliers, so I think it's working well as is.
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