Bibor
Doomsday Machine
now compare between the two processes , and you can see that Economy is not involved in expansion in Civ5.
I know there are Hammers,Science,Gold,....etc in Civ5 which is obvious , But The whole Economy does not affect Expansion directly and does not affect research. Everything is related to happiness which makes the gameplay dull as in:
Expand to 4 cities -> hook up resources -> Expand To 6 cities -> Build Circuses -> Expand to 8 cities -> Build Colliseums -> Expand to 10 cities -> Trade away surplus
How can happiness and science not be a part of an economy? Economy is not equal to finances. Economy is the total output of a nation's workforce. Financially speaking, Research Agreements is gold converted into science, and so is rush-buying science buildings. And rush-buying is not an added feature like it was in Civ4, it's an essential part of gameplay, much like whipping was in CIV4. Also getting new happiness is not a dull process, believe me. It's sure as hell more exciting than making a worker plant 3 floodplain cottages.
If you really need an example, I rush-buy Colosseums in old cities to sustain new cities on a regular basis, often with money gained from selling away happiness resources (10 GPT from a happiness resource pays off after 30 or so turns of having the colosseum, considering the saved-up hammer costs and 3 gold ukpeep).