civilization-5
In Civilization 5, each city you build increases the cost of new social policies by some percentage, based on the current map size.
This question mentions +30% for duel sized maps. I'm assuming this is correct?
What are the percentages for other map sizes?
Although bwarner's answer was helpful as always, no one verified beyond "I think so" that puppet cities are affected by each of the civilization wide effects, so I did some testing and:
Yes, puppet cities are affected normally by all civilization-wide effects.
I can't verify that there are no exceptions, but I verified at least one of each of the things I was concerned about...
Civilization Special Trait
I loaded up France on easy, and went about conquering. Japan fell, giving me Kyoto to play with. As soon as I conquered the city and took it as a puppet, it was producing 2 culture. This matches perfectly with France's ability, so CHECK!
More Test Setup
Having acquired my victim, I setup the test: social policy ready, golden-age ready, and wonder ready all on the same turn! (Save file available upon request, whenever I get around to it after that.)
Before
Social Policy
I enacted Liberty->Republic, which gives +1 production/city. That matches, so CHECK!
Golden Age
I already had culture working for me, so I started the golden age by enacting the social policy Piety->Reformation. Clearly shows an increase in both gold and production, CHECK!
World Wonder
If you take a look at all of my cities from the same turn, you can see Orleans is about to finish the Sistine Chapel, which gives +33% culture/city. I went to the next turn, and without any growth or buildings completing, the after shows increased culture on Kyoto. (Lyon also started with 7 culture and ended with 9 as well, so the rounding definitely matches.) CHECK!
Everything checks out. I suppose puppets really are just normal cities that you don't control. I would still love to hear if anyone finds any exceptions!
Actually I think in some cases it still might be not such a bad idea to do that. Especially if you didn't invest too much in that policy and you are not going for cultural victory anyway. Some early game policies matter much less in the late game. For example you can use a bit of Liberty for early expansion and then abandon it for Autocracy.
Best Answer
This is taken straight from the XML files included with Civ V: (Updated for the June 2011 patch, where all of them were reduced by 50%)
So it's 15% for all but the largest two map sizes.