I once thought it had something to do with secrecy of indicies of various types. I was about to get all indignant about the assumption of openness in states that might identify with a particular economic method.
It seems to me that government type meaning something might be interesting. Although I think that a simple choice from 6 options would be inappropriate and mundane. Perhaps something where you have 6 (or so) variables such as tax regime (essentially tax rate), freedom of information (indicies available, productivity), freedom of travel (im/emmigration, productivity), centralisation of buearacracy (ratio of size of captial to cities), personality cult etc.
Each variable could affect various things, such as bonuses to productivity (welfare led?) which might be offset by greater consumption of certain products (such as more internet required for countries with more freedom of information or more cars for more freedom of travel etc).
Any description of national government is always more appropriate when done multidimensionally.