The fertility replacement level is roughly 2.1 children per woman. This means each women becomes a mother and has at least one daughter who can also have children.

The birth rate in South Korea and some countries is at 0.8-1.2. This means fertile women are averaging half of fertile daughter.

However, there is a U shape in the fertility statistics. Statistics show fertility declines with rising income to certain level but in high-income we see a reversal. Fertility dips at low-to-middle incomes but rises among the affluent and rich. In the US, families earning $700,000+ have a TFR of ~2.0 vs. 1.8 for $80,000 household. This is almost replacment and is a 0.2 gap that's widening.

A 2024 estimate is for ~600,000 individuals with AGI (Adjusted gross income) at over $1 million in a year. This group grew 10–15% from 2020–2024, driven by tech, finance, and executive pay. They have been living in California (100,000+) and New York (~80,000) but there is movement to Texas and Florida and other places.

American billionaires have seen a fertility surge. The top 0.0001% average 2.5–3.0 children, up from 1.8 in the 1990s, driven by access to surrogacy, nannies, and cultural emphasis on legacy.

For the highest-earning individuals, the opportunity costs of having children become less of a constraint. They can afford extensive childcare, household help, and other services that reduce the burden of child-rearing. The family can afford to have one or both parents not work.

In 2025 reports estimate, there are approximately 6 million U.S. millionaires and around 58 million millionaires globally. For ultra-high-net-worth individuals (UHNWIs) with $30 million or more, there are about 234,000 globally. Most UHNW are in the USA.

The World Inequality Database and UBS estimate ~1.8 million people with pre-tax income > $1 million in 2024. This is 0.03% of the global adult population (5.4 billion). Estimates vary due to underreporting in low-tax jurisdictions. If using PPP-adjusted income, the number could dip to ~1.5 million and tax-inclusive models push it to 2.5 million.

AGI Tech abundance could boost the world by ten and even 100 times. This happened with the industrial revolution over a one hundred year time frame.

Epoch.AI has an automation model of the economy where the 100X boost happens by 2040.