I read a bit about the world population, and it changed throughout the ages. I wanted to see, whether the development of the population in Civ IV is realistic, or there is room for improvement. At 1000 BC, the world population is estimated to be between 50M and 115M. At 0 AD, it is between 150M and 300M. So, the world population is almost tripled in 1000 years. However, between 0 AD and 800 AD the population stagnates. It is estimated between 220M to 330M. Even at 1000 AD, many estimates indicates a population of only about 250M. Until 1500 AD, estimates lies around 400-500M. Ok, how should this be interpreted? In the game, the most significant increase in population comes with peasant servitude, which is on of the earliest middle age technologies. So, it would be researched at 5th or 6th century. However in reality, peasant servitude and feudalism didn't seem to have contributed much to the world population. In fact, the invention of iron tools and irrigation systems and so on seems to have a much greater effect (I am not a historian btw, an opinion from a historian would be much better here.). From 1500 AD on, the population starts growing rapidly. Some scholars mention that the crops that were brought from Americas have contributed to the population growth in Europe and Asia. This is actually great, since Civilization can simulate this fact very well: New crops, and fruits, and luxury resources from an other continent increases health and happiness and boosts the population in the game. The population reaches 1000M in 1800 and 1650M in 1900. Today, it is about 7400M, which shows that we should slowly stop breeding as mankind But the joke aside, it seems the population benefited most from farming mechanization and the advancing medicine in the 20th century. This is also modeled well in the game. In conclusion, I think the peasant servitude and serfdom should be slightly nerfed, the increase of between the classical and medieval ages should be somewhat milder. One interesting note: In 1800 only 3% of world population lived in cities. This proportion has risen to 47% in 2000.