This is true only if we assume childbearing is constrained by available resources
No, it’s not. We only need to assume that people have more preference for a child when the child would live in a world with more resources. The resources don’t have to be low enough to affect the chance of the child’s survival. If someone is more likely to have a child if the child could live an upper middle class lifestyle, and one less person means there’s a marginally greater chance that the child could live such a lifestyle, the effect would happen.
“Constrained” may have been a poor choice of words, but I still don’t think that’s a good assumption. It’s plausible that people are more inclined to produce children when they expect them to be economic assets, but outside of a fully exploited subsistence environment I don’t expect that to depend linearly on population. And even if it did turn out to be linear, I don’t think our instincts are accurate enough to make that determination without something extremely simple and obvious (like remaining land area for farming) to cue off of.
Note that richer countries have fewer children per capita than poor ones, and richer demographics within those countries tend to fewer children than poorer ones. There’s some confounders like infant mortality to deal with, but even so this would be strongly antipredicted by your theory.
(On the other hand, I’d be willing to believe that a given set of parents is likely to want a certain number of children, and to produce more up to that number, fertility allowing, if one unexpectedly dies. Inheritance and other family-controlled resources can play into this, but it remains a purely local phenomenon.)
Note that richer countries have fewer children per capita than poor ones, and richer demographics within those countries tend to fewer children than poorer ones.
I can think of several reasons offhand why rich people would have fewer children:
The lifestyle conducive to being rich makes the parents more likely to delay childbearing, possibly leading to having fewer children.
Rich people are smarter, more educated, and/or have better impulse control and therefore are more likely to use family planning properly.
Raising a child is disproportionately costly for richer people—they may spend lots of money on the child for things like college educations, and they don’t have jobs such as farming which would let them benefit from using the kids as manual labor.
The first factor applies to the degree that becoming rich is controlled by the parents’ actions. The second applies to the degree that being rich is associated with the parent’s traits. And the third applies to the degree that the parents want to achieve a particular level of wealth for their children and need to spend money to do so. Having the children become marginally richer because of factors that are not related to the parents’ actions or traits and do not involve spending money on them would not lead to that marginal increase being correlated with having fewer children.
No, it’s not. We only need to assume that people have more preference for a child when the child would live in a world with more resources. The resources don’t have to be low enough to affect the chance of the child’s survival. If someone is more likely to have a child if the child could live an upper middle class lifestyle, and one less person means there’s a marginally greater chance that the child could live such a lifestyle, the effect would happen.
“Constrained” may have been a poor choice of words, but I still don’t think that’s a good assumption. It’s plausible that people are more inclined to produce children when they expect them to be economic assets, but outside of a fully exploited subsistence environment I don’t expect that to depend linearly on population. And even if it did turn out to be linear, I don’t think our instincts are accurate enough to make that determination without something extremely simple and obvious (like remaining land area for farming) to cue off of.
Note that richer countries have fewer children per capita than poor ones, and richer demographics within those countries tend to fewer children than poorer ones. There’s some confounders like infant mortality to deal with, but even so this would be strongly antipredicted by your theory.
(On the other hand, I’d be willing to believe that a given set of parents is likely to want a certain number of children, and to produce more up to that number, fertility allowing, if one unexpectedly dies. Inheritance and other family-controlled resources can play into this, but it remains a purely local phenomenon.)
I can think of several reasons offhand why rich people would have fewer children:
The lifestyle conducive to being rich makes the parents more likely to delay childbearing, possibly leading to having fewer children.
Rich people are smarter, more educated, and/or have better impulse control and therefore are more likely to use family planning properly.
Raising a child is disproportionately costly for richer people—they may spend lots of money on the child for things like college educations, and they don’t have jobs such as farming which would let them benefit from using the kids as manual labor.
The first factor applies to the degree that becoming rich is controlled by the parents’ actions. The second applies to the degree that being rich is associated with the parent’s traits. And the third applies to the degree that the parents want to achieve a particular level of wealth for their children and need to spend money to do so. Having the children become marginally richer because of factors that are not related to the parents’ actions or traits and do not involve spending money on them would not lead to that marginal increase being correlated with having fewer children.