Statistically, governments around the world can be used as a baseline
0: Somalia in the 1990's: Model of decency? Nope! Hopelessly corrupt
Afghanistan in the period before Taliban ascendance: If you are not part of the clan, you're screwed
1: No real examples of large scale. But look at Tamany Hall, 'company towns', etc. Very high
2: Either steadfastly honest as they want to work together or on their way down into a type 0
3: Only recourse for of a redress of grievance is appeal to the mighty. Very corrupt
4: Power is separated from direct input by the people. Take a look at the UN's listing of least corrupt countries and every single one of them is a democracy
5: No examples to speak of. As long as it IS a meritocracy, the choosing of people who are skilled (as opposed to connected) would be more likely to produce honesty
6: Depends. Either hideously corrupt (cruel administrator), moderately corrupt (appeal to mighty again) or minimal but still nasty (Pinochet's regime, while brutal, was far less corrupt than most in South America)
7: Let's use all Earth as an example: We have Libya on the UN Human Rights Commission, we have China and France blocking any resolution on the Sudan
8: Generally, type 8 more or less represents a 'good' bureaucracy to type 9's. Things may require excessive paperwork and procedures (hey, a new RPG) but once filled out, the system flows
9: As above, but more like a socialist state. The old Russian joke goes 'they pretend to pay us and we pretend to work'
10: Charismatic does not mean likeable. Charismatic means above the law. Rampant corruption until the big guy decides to clean house. Then everyone is scared. For a few months and then he puts his friends in. This would be Stalin or Hitler: they do what they want to whomever they like
11: A dictator with limits. Sort of like a knee in the crotch without spiked knee pads. It is better but not by much. The non-charismatic implies that their power does not necessarily transcend the law. Franco or Pinochet were this.
12: Like the dictator but diffused among a group. Now you have the possibility of power struggles. More corrupt
13+: Ah, the theocrats. Religious governments may be hard to classify. While some are brutally honest, they are VERY unpleasant to deal with (Taliban). Others may be corrupt AND unpleasant to deal with (Pol Pot's Khmer Rouge. Communism is a religion of the here and now and the way these guys practised it would have made Tomas de Torquemada flinch)
Sum up: Use the Megatraveller book Hard Times. They rated government types by franchise
2D-7+Franchise will give you your corruption rating with a few (2, 8, 11) requiring a second die
1-2 add 1D
3-4 as is
5-6 minus 1D