And, what will be the U.S.'s population?
There really are too many variables to answer that question in any meaningful way… a demographer might expect present trends to continue, but no estimate can be made past 2050 with any value.
The most important factors in my view could be:
the Energy budget of the world and how much will be available to support the human population-
this could be affected by the lack of fossil fuels, and the rate of replacement by solar or nuclear power;
The way in which wealth is distributed -
poor people, if any still exist in 2303, might continue to have a high fertility rate- if the proportion of poor people to rich people is large, the poorer countries will probably suffer repeated malthusian collapses;
On the other hand a world with easy access to energy, resources and opportunity would be likely to spontaneously develop a low fertility-/replacement rate and there could be distinct shortage of young people.
The age and vitality of the population-
if there are several technological breakthroughs in life science (as expected by many forecasters) the population may be on average very much older than today. This would cause a growth in population by itself, and would need to be countered by a drastic fall in the birth rate. It may be that the period of fertility is extended, in which case a proportion of the population may no longer feel the pressing need to reproduce before they are thirty;
Dramatic events like plagues and warfare-
both of these things could be made much worse by technology and or human stupidity. A genetically tailored virus could be released accidentally or on purpose- ditto atomic or nanotechnological holocaust.
Wars may on the other hand be fought with combatant-specific weapons and have fewer casualties, possibly becoming more frequent for that reason.
Finally in three hundred years advanced technology might allow some or many people to upload into an electronic medium, occupiying relatively little space and consuming few resources…
personally I do not anticipate this development having a significant impact on population levels, especially not for many centuries to come-
but I could be wrong about any of this…
Sci-fi worldbuilding at
http://www.orionsarm.com/
The definitive answer is somewhere between 0 and 10 billion people. Probably.
Can i change my question to 100 years?
…assuming current trends (global warming, resource depletion, clean water) continue and no significant new ones arise.
I am not trying to look forward into the future here in General Questions obviously. I just want to be able to grasp how long things can go on like this. Like, where is our current situation going to take us?
http://www.iht.com/cgi-bin/generic.cgi?template=articleprint.tmplh&ArticleId=90067
The latest UN estimates actually suggest that world population will peak mid-century (just shy of 9 billion), then decline. Growth rates are dropping in most developed nations; the US is not one of those. We are expected to keep increasing in size, from 285 mil to 409 mil by 2050. If we stay at that rate (or slightly lower), that would put us at around 500-600 million, with a world population of less than 9 billion come 2100.
But estimates were made to be revised. And these are just median numbers.