The Wealthy Have Fewer Children. Why?

It's a global trend: the more developed a country becomes, the lower the proportion of its young population and the higher the proportion of its elderly.
The old Japanese proverb, "The poor have many children," applies perfectly here.
It's a universal tendency for the poor to have more children and the wealthy to have fewer.
Perhaps the wealthy, rather than dedicating their lives to raising children, are more inclined to enjoy their own lives. This is a plausible explanation.
In other words, the wealthy, seeking greater freedom and affluence, prioritize enjoying their current lives over investing energy in child-rearing.

Japan's Aging Rate is Twice America's

Let's compare the age structures of Japan and the U.S. The proportion of the working-age population, typically defined as 15 to 64 years old, is nearly neck-and-neck: 65% in Japan and 67.1% in the U.S. However, the situation changes dramatically when we look at the elderly population aged 65 and over.
At 21.5% in Japan, compared to 12.4% in the U.S., the elderly population in Japan is roughly double that of the U.S.
This suggests America's youthful vitality. These figures are from 2007 for Japan and 2005 for the U.S.
Population growth is particularly notable among non-white demographics in the U.S., and within 40 to 50 years, they will outnumber the white population. In essence, it is certain that people of color will constitute more than half of America's population.

America Can Be Called Youthful

America is bound to change. While the U.S. holds overwhelming global power in politics, economics, and military strength, the transformations it will undergo in the future are points of great interest and concern.
What can be said is that despite talk of America's decline, the existence of the U.S. dollar as the global reserve currency will continue for some time. While alternatives like the Euro or the Chinese Yuan are often discussed, the reality is that no currency has emerged to replace the dollar. We cannot afford to look away from the dynamic shifts in America.