7 city sizes are allocated according to their GDP's (which are calculated from populations and GDP per capita values. Used more detailed numbers such as GDP per capita from individual provinces/states, whenever I found them.)
10-20 $bn = 1 income (eg. Tblisi, Sofia)
20-40 = 2 income (eg. Warsaw, Baghdad)
40-80 = 4 income (eg. Stockholm, Munich)
80-160 = 8 income (eg. Rome, Barcelona)
160-320 = 16 income (eg. Madrid, Istanbul)
320-640 = 32 income (eg. London, Paris)
640+ = can be recorded individually (New York, Los Angeles, Tokyo)
Capitals are red or yellow (no difference - just for visibility)
The numbers show what I decided to name rural industry (most of the GDP of rural areas go to agricultural stuff consumed at home anyway, so this is a fraction of the actual rural GDP. I decided on it kind of arbitrarily as 10%. So in rural areas $100bn = 1 point)
USA does not have any size 1 cities, because it actually has 90 of them. The number for US is rural income of 24 + 90 income from size 1 cities (it seemed too much work to place 90 cities, after placing the 70 or so larger US cities on the map)
Plus each country has a base of 1 income on top of everything.
so Albania has 1, Bulgaria 2, Romania 4, Hungary 6 income shown on the map.
Some extra rules might be needed to offset the unrealistic disadvantage of some nations (North Korea) due to their low GDP on paper. Iraq may also be too low due to the current situation.
http://www.civfanatics.com/gallery/showimage.php?i=1830&original=1&c=member&imageuser=89317