By 2040, 100% of U.S. population growth will come from immigration (source US CBO, and also see the main page). This one of several posts on this topic.
They further forecast that immigration will add roughly $1 trillion to the US GDP each year over the next ten years – but acknowledge their estimates may be highly uncertain.
Realistically, if you add more people – earning incomes and spending money, then there will be more economic activity and logically the GDP will be higher. This is not magic or anything special.
In the early 1970s, 4.7% of the U.S. population was foreign born. Today, 15% of the U.S. population was foreign born. The CBO does not estimate what that will be in the future but would not be surprised if 20+% of the population is foreign born by mid-century.
Imagine the enormous culture changes that may occur in the U.S. as we move rapidly to a very different mix of backgrounds, country origins, life experiences, languages and cultures. Obviously, some, perhaps most will be positive – but there may also be some negatives.
