When I was born (1 generation ago) the U.S. had around 220 million people. We now have over 300 million people. That is roughly a 1/3 increase in 1 generation. Last time I checked we have not acquired any new territory. The only conclusion that I can come up with is that we are more crowded now than we were then. I really want to get to the bottom of this so let me know where my logic is flawed.
You have probably heard of the baby boom of the 50s and 60s. This high birth rate takes a while to work its way through the 75 year average lifespan. Which means our population will continue to go up until the baby boomers begin to die off in quantity, even when we’re presently below replacement rate.
Obviously, a baby born this year does not begin to reproduce this year or next, so there is at least a 20+ year lag before changes in birth rate begin to significantly impact total population numbers. What does begin to change very rapidly is the number of people in each age group. There are far fewer children as a percentage of the population than there were 30 years ago, and a great many more elderly. When those elderly begin to die in large numbers, population growth will slow and then go into reverse.
If there were no immigration, legal or illegal, we’d be slightly below replacement rate at this time. We do have immigration of both types, of course, and their presence and that of their offspring is a significant contributor to our population growth in the last 20 to 30 years.
Estimated population in 1980 was 227M.
BTW, another reason for the growth in population is that people are living quite a bit longer today.
We have had nearly 60 million abortions. The birth rate per family has declined. Add to this a declining global birth rate that will reflect negative growth in Europe and North America by 2020.
Where do we go from there to demonstrate the source of increased population? Is there any possibility other than increased immigration?