okay I have another question. Once again, monarch/epic. I took a 6 month break or so, and I want to know if slavery is still super strong, and how best to use it. I usually just wait until it only costs 1 pop, and unhappy for 15 turns. It doesn't seem to be so gamebreakingly important like everyone says it is though.
I agree with Lord Parkin. It is generally accepted that it is better to whip two or more population points. As you play at epic speed, the unhappiness lasts for 15 turns. He is also right that the removal of a bug associated with the hammers you get from whipping has slightly decreased its efficiency when you were abusing the bug before. The removal of the bug doesn't have a big effect if you were unaware of the bug and weren't abusing it.
How to whip the most efficiently:
1) Whip just before a city is about to grow into unhappiness.
Why? Because a size 6 city with a 46/48 foodbox changes into a size 4 city with a 46/42 foodbox if you whip 2 citizens. So you'll get a nice food overflow. Upto that moment you were using the maximum number of citizens the city could maintain within the happiness cap which is efficient. It is less efficient to whip after getting unhappy because you won't get the food overflow. It is less efficient to whip earlier because you won't use the maximum number of citizens as long as possible.
2) Whip 2 (or more) citizens each time.
Why? Because it takes time for the unhappiness to wear off (15 turns at epic speed) and during that time, your city can regrow. If you only whip one citizen, then you'll regrow quickly and have 1 unhappy citizen due to whipping unhappiness. If you whip two or more, then the unhappiness will wear off while regrowing. If you whip 2 citizens at the moment that I mentioned in the post above, then you will actually only be 1 pop under the old happy cap after 1 turn and because of the happiness penalty of whipping, you're at the happy cap. Each whipped citizen will give you 45 base hammers which are effected by the production bonusses in the city.
Usually it is less efficient to whip more than 2 citizens. The reason is that it takes too long to regrow upto the old happiness cap. However, if the city is growing quickly (large food surplus + granary), then it can be more efficient to whip more than 2 citizens.
3) Use a granary in cities where you whip.
Why? It allows you to regrow upto the old happiness cap more quickly and thus is more efficient.
Whipping with a granary allows an efficient conversion of food into hammers.
For instance: Your city with granary is size 4, foodbox almost full and decides to whip a worker. It takes 44 food to get back into the city at size 4 with an almost full foodbox, but you get 90 hammers now. Note that you aren't using one citizen for 15 turns.
4) Whip units like workers and settlers.
Why? If you build them, then you're converting 1 food into 1 hammer. If you whip them with a granary, then you have a better conversion factor as you can see above in point three.
People who are crazy about whipping will often mention the very good food-hammer conversion factor. They often don't seem to realize that you're not using a tile for 15 turns. If a city can't regrow quickly enough, then you're losing a tile for more than 15 turns. If a city doesn't have a granary, then the food-hammer conversion that is achieved by whipping isn't that great if you consider that you're losing a tile for 15 or more turns.
Whipping is good and it is the only way to use the extra food that cities are producing while they are getting near their happiness cap. But you have to know when to use it. It is absolutely horrible to use a 4 citizen poprush in a size 8 city which only grows at 2 food per turn and doesn't have a granary.
You can only whip half the citizens of a city. If the building/unit is more expensive than the hammers provided by those citizens, then you can't whip. Whipping small and great wonders is usually very inefficient. You get less hammers for each citizen when whipping these things.
Whipping can get you some things which you'd rather have now than later. For instance a defending unit in a city that is under attack or a granary in a city that has to grow a lot or a lighthouse in a city that will use lots of coastal tiles. Don't whip things without any hammers invested in them (during the first turn of construction). You will get only 2/3 of the hammers from each whipped citizen in that case (30 per pop at epic speed).
Good luck whipping and welcome back to civ!