I was wondering what people think the population of the United States is in 2281; and what the population of the word is.
It seams that most people preferred the relative desolation of Fallout 3 to the "crowded" New Vegas. I preferred the desolation as well. However I am conflicted in which game better represents the population of the broader fallout world. If all 122 vaults were filled to capacity (which they were not) and we assumed that each vault opened after an average of 100 years and the population from the vaults grew at an annual rate of 1% (vaults are assumed to contain 500 people) it would give us a little less that 183,000 people. This rate of growth is close to Americas current one. A 10% growth rate renders freakishly high numbers. I think that the vaults would even struggle with the 1% rate because the average age of a vault dweller would likely be too old to have children. Considering the population of the NCR and even the capitol wast land; it would seam that more people survived out side of the vaults than inside them. Lastly I was thinking that the new technology in Fallout is close to that which existed in 1870 to 1910 time frame but on a very low scale of production. Which means no large scale mechanized farming. In this period of time between 30% and 40% of the population were farmers. I was thinking that this would mean that even a strictly military faction would need that many more people just to stay operational not to mention the number of people who would be either too old or young to work or employed in non soldier jobs.
Ken
According to a population census in 2241, the population at that time in the NCR was at 700,000 people. Hugs 
"Say 'ello to my little friend!"
An interesting question. Although the fall-out 3 says that those who survived the holocaust did so in great underground vaults, I suspect that this isn't entirely true. The survivalist survived the apocalypse without a vault and I suspect that there are likely many tribals who survived mainly because of rural isolation during the great war. The New Vegas area seems to be heavily populated because of vast economic power, access to clean drinking water, medicine, high-levels of immigration and military intervention.
In terms of demography the Mojave is probably an extremely high population center in post-apocalytic America, outside of the NCR itself it is probably one of the most heavily populated areas in the West.
DC, however is very different, it is overran with super-mutants leaving most of the city infrastructure unutilized, the only available water supplies available are irradiated which profoundly limits population growth by creating low agricultural yields, high death rates and high infant mortality rates. The most populated areas are besieged rural settlements and half of a carrier, most of the rural wasteland is too dangerous to cultivate. Much of the working population of reproductive age is enslaved which also profoundly impacts population growth.For instance the brutal working conditions of Caribbean slave colonies often created conditions where the average life expectancy of a slave was 7 years.Since, it takes more than seven years to bring children to working and reproductive age, it only took a few years for a slave colony to begin to depopulate, thus new blood was constantly needed to keep production up. The constant slave importation in the pit seems to echo this situation. DC also seems to be a prime region for slave capture and exportation to other areas like the Pitt.
The awesome thing about DC is that depopulation feels like it's continuing inexorably and civilization in the area is on its last leg.
Vegas and the NCR are different, they are rising civilizations that have been placed in very favorable circumstances and can exert enough power at-least to settle much of the land. Most of their populations are free and slaving is relatively limited, Caesar seems to have left most of his slaves behind the frontline (probably so he doesn't have to fight the ncr and a slave revolt).
While working technology is limited, the NCR and Vegas are both reindustrializing, and they both have access to medicines, agricultural techniques,and technology that was not available in 1870. Their populations are small enough to make use of the enormous bounty that has been left behind.
Most of the NCR is engaged in agriculture, however industry and extremely wealthy brahmin barons are displacing the rural population of the NCR which means there are spare hands enough to yield a large army. House has robots and the legion has a huge army of slave labor which would have to outnumber their fighting force
--Boredintheusa 06:17, February 9, 2012 (UTC)
We think the total for the entire U.S., including the conquered Canada, would be in the tens of millions. Most of North America would not have been as heavily bombed as D.C. and the other major cities. Just consider thousands of areas like Point Lookout (location), (Swampfolk are people too, just like us rednecks, ya know).DarthOrc 07:15, February 9, 2012 (UTC)
What about Project purity and the Brotherhood? They certainly are going to change things. i wont be surprised if the brotherhood decide to move their head quarters to the capital wasteland.
- Why? The brotherhood as a whole have no interest in it. Libery's a wreck they have no hope in rebuilding, and the purifier isn't any use to them. Agent c 01:47, June 19, 2012 (UTC)