Without knowing Keith had made the chart above, I also made a chart to try and hone in on this concept.
That said, I think graphing systems on a chart like this will always get pushback unless it's made with real data, and even then I doubt it's worth sharing...
In any case, single winner elections which elect plurality winners will always have lower PR than those which ensure at least majority support, and methods which take into account voters secondary and tertiary preferences and level of support for other methods will also have a higher level of PR.
Can anyone think of some better multi-winner methods that would qualify as semi-proportional?
It's worth noting that an electoral system with no PR is possible (dictatorship) and perfect proportionality is also possible if a given election had everyone neatly assigned to a viable sized team, but I focused my chart on the actionable and democratic section of the spectrum.