Essay #03
The household Malthus
Between 2006 and 2021 South Korea budgeted roughly 200 trillion won to persuade its citizens to have children. The birth rate it arrived at was 0.72 per woman, and 0.55 in Seoul. Nobody in a rich country today gives "there is nothing to eat" as the reason for not having children, and yet fertility sits pinned at the lowest levels ever recorded, and money has not moved it. Something underneath the money is setting the number.
In 1798 an English clergyman named Thomas Malthus published an essay arguing that population would always press against the food supply. People multiply faster than fields can be made to yield, so every advance in living standards would be eaten up by more mouths, and famine, disease and late marriage would push the population back down to what the land could feed. He was not wrong about the world he described. In an economy that ran on nothing but the sunlight that fell that year, output was bound by land, and population was held down by whatever physical constraint bound hardest. Then synthetic fertilizer arrived, made by pulling nitrogen out of the air, and food stopped being the limit. Malthus's logic survived; what changed was the thing doing the limiting.
Where the bottleneck is now. The price of almost anything is set, roughly, by the cost of energy, of manufacturing, of transport, of computing, and of whatever labor has not yet been automated away.
That last item has a proper name in economics. When wages rise in a sector where productivity is rising, every sector that hires from the same labor market has to raise wages too, or it cannot hire at all. Education, healthcare, childcare, elder care: their productivity has not risen, their wages have, so their prices climb without end. The economist William Baumol called it the cost disease in 1967. The sectors he named are almost exactly the ones a child is bought from.
Figure 4-1 What got cheaper, and what did not
| Item | Change | Index 2024 (2000 = 100) |
|---|---|---|
| Hospital services | +249% | 349 |
| College tuition | +185% | 285 |
| Childcare | +134% | 234 |
| Housing | +95% | 195 |
| Average (CPI) | +85% | 185 |
| New cars | +25% | 125 |
| Clothing | -5% | 95 |
| Software | -70% | 30 |
| Toys | -70% | 30 |
| Televisions | -97% | 3 |
Log scale, so equal slopes are equal rates of change. Baumol sectors rise; automated goods collapse. Label positions on the right are spread for legibility; the line ends are exact.
Source: US Bureau of Labor Statistics, consumer price data, 2000–2024.
Since 2000, American hospital services have risen about 250 percent, college tuition about 185 percent and childcare about 135 percent, while televisions fell 97 percent and toys and software about 70 percent each. Everything automation reached collapsed in price. Everything it did not reach, the services one person performs for another, soared.
Raising a child means buying, for twenty years at a stretch, precisely the goods automation has reached least. The constraint on population today is the price of a child rather than food. That is what I mean by the household Malthus.
What follows. If that is right, falling fertility is a price phenomenon rather than a cultural one, and there is a test: does paying people change it? Korea ran the test. Fifteen years of spending, on a budget line that grew more than fortyfold, left the price structure exactly where it was, and the birth rate with it.
Values are not the first cause. They appear two or three steps downstream of a structure that sits underneath them. Energy and technology set the prices. Prices set the household's budget and its anxiety about the future. Under that budget, households choose career over children, which is rational, and later the choice acquires the name of a value. To notice a change in a downstream variable and call it the cause is a little like calling the movement of a thermometer needle the cause of the heat.
The strongest evidence on the other side deserves to be stated plainly. Compare American states since 2007 and ask whether fertility fell faster where unemployment, house prices, childcare costs or student debt were worse. It did not, or not by much, and the authors conclude that a generation's priorities shifted. There are two replies. A shift in priorities is not the end of the explanation but the thing to be explained, and when the priorities of a whole generation move together, that looks like a cohort adapting to the price system it grew up watching. And the two studies are asking different questions. How much births move when one price is nudged within today's system is not the same as what happens when the whole price system changes. The Korean payments tested the first; only the second can move the number.
The largest case. China's births fell to 7.92 million in 2025, down 17 percent in a single year and less than half the figure for 2016.
That the decline will not reverse is already settled, and not by policy. Women aged 20 to 34 account for roughly 85 percent of births, and their number falls from 105 million in 2025 to 58 million in 2050. Since births spread from about age 18 to 40, every woman who will give birth in 2050 has already been born, or will be by 2032, so the population base is fixed and the only degree of freedom left is the fertility rate, and holding it where it is still takes births in 2032 down to around 6.5 million. A country of 1.4 billion would then be producing barely more children than a country a quarter its size.
Of all the variables in this story, population is the one fixed earliest and the one that moves last.