[thestranger]

I'm confused as to what is being shown in the first graph. How can the number of party rounds be greater than the total number of rounds in some places? Why does the y-axis have different numbers on the left and right sides?

[twic]

The axis on the left is for the blue party rounds line, and the axis on the right is for the red total rounds line.

I assume this is because party rounds have never been more than 3.7% of total rounds, so showing them on the same scale would have left the party rounds line rather hard to glean anything from.

A better approach would probably have been to express the counts as ratios to their 2005 values; they could then have been presented on the same scale.