Besides economy, the other battle I was fighting was to stay under the domination limit. With 10 AI civs to start, the dom limit was a fairly tight 56%. And even once I stopped founding cities, Sid's Sushi still accumulated some flips as always.Besides economy, the other battle I was fighting was to stay under the domination limit. With 10 AI civs to start, the dom limit was a fairly tight 56%. And even once I stopped founding cities, Sid's Sushi still accumulated some flips as always.
So I had to give away some cities. I'd planned for this all along, to give my southern cities over to Egypt at this time. I'd mostly just built units out of these cities rather than buildings.
This was the right thing to do. Inland cities like this might occupy 15 or 20 land tiles per city. Giving that away let me annex 15 or 20 island tiles instead, which could hold three or four cities instead of just one. The goal was to occupy every possible island tile and keep just enough of the mainland to stay under domination until I was ready to win. I topped out at 150 cities total, about 145 of them with Sid's Sushi excepting a few border cities that weren't supposed to culturally grab land.
So my population and score rose, and rose, and rose... and inevitably finally did slow down. I'd been using my score calculator to project ahead, and saw that it took about 20 population gain per turn to break even against the reduced exponential bonus. With 140 cities, that means I needed one out of every seven cities to grow each turn, or equivalently that the average growth interval across all my cities was seven turns. Presently that was no longer true, and on the turn roll to 1030 AD, my score actually dropped very slightly. Time for the final fireworks.
As ever more markets and grocers continued to complete, and cities parked on Wealth, I suddenly had loads of income again. I had also trickled research at 0% to Rifling (by Sankore and neglectfully auto-hired scientists), and conveniently somebody researched Military Tradition for me to steal. Now I started cash rushing cavalry (still with Kremlin) in homeland cities. On the last turn, I would conquer as many cities as possible to slingshot past the domination limit.
The diplomatic situation had gotten tangled. Qin peace-vassaled to Gandhi, and Victoria peace-vassaled to Ramesses, and Gandhi and Ramesses even defensive pacted. So to declare war on any of these opponents meant declaring on them all. But I could handle that, with a total of almost 100 cavalry, including a few ancient immortals upgraded.
My own culture borders with railroads, plus the fact that I'd previously owned the cities gifted to Egypt, meant there was a lot of mobility available for the cavalry to reach quite a few cities in a single turn. I captured eleven cities for a total of 101 population on this final turn, tacking on a nice extra 75k score! I also traded for Astronomy and Physics on the last two turns for the tech points. Yes, expiring the Colossus cost over 3000 income.
One last scroll-through to micromanage any city possible into growing this turn, and one last overview.
Domination Victory in 1040 AD. 4412 is the final population number, and the other score components are in the shot too.
And the demographics. (Not quite final, that's from right before declaring war with the Sushi and Mining imports still active.)
Notice that there was still quite a bit of growth headroom. 11760 food means 5880 potential population, although I actually only had 4400. Didn't have time to convert that surplus food to actual population, with the ticking clock of the decaying exponential bonus. I'm amused by that Population number, which we all know is a silly cubic formula, but it's satisfying to go way over a billion there and two billion would have come shortly too.
The food graph pretty much tells the story, showing clearly where Sid's Sushi was founded. The zigzag is where I had to self-pillage some Sushi resources to avoid bankruptcy, then the steeper slope a bit later is hooking them back up. The total food production leveled off pretty quickly once Sushi was fully spread. I think this goes to proving the earlier point: the key is spreading Sushi as fast as possibly possible. Just dry-whip and dry-rush executives, the turn economy is that important.
I'd share the GNP and production graphs too, but they look essentially identical to that food graph.
Why "Sushi Sigma"? I needed some way to differentiate between attempts at this challenge, got tired of numbers, and started picking arbitrary Greek letters. No real meaning. 
Did I forget something? Where did the score end up after all of this? What do you get for 4400 population where the "max" is 1500, and for doing it in just over 500 turns on marathon? I'm going to make you click one more time for the final reveal. 