It happenes every game - I decide to raze a city or a metro because I need the 3-4-5 'slaves' for which no maintenance is necessary. The number is something like the pop devided by 2 rounded down (BTW what is the exact formula?) However I may also raze a city say size 7 and not get a single worker. Why? Does it depend on my government? on his government? on whether(how many) native workers I have? I am totally clueless and any sage advice/formula will be deeply apreciated!