Torie, I don't want to sound stupid, but what are chops and erosity?
I'll answer. Chops refer to the number of times that political units are divided between districts. If a political unit, for instance a county, is split between two districts then it has one chop. If it's divided between three districts then it has two chops.
Erosity is a measure of how irregularly shaped a district is. It comes from the word erose: having the margin irregularly notched <an erose leaf> (merriam-webster.com). Rather than just measure the perimeter of a district, erosity recognizes that small irregularities in an urban area are just as important as large irregularities in rural areas. Following a recognized political border that is itself irregular doesn't count towards erosity any more than if the border were a straight line.
A good neutral redistricting plan generally reduces the number of chops and reduces erosity, though at some point has to make a trade off between the two. The measures have been developed for our redistricting discussions on this board over the last 3-4 years.
I understand. But what is the difference between erosity and compactness? A distinction between perimeter and area?
