Dachs said:
first one of these doesn't always correlate well with low birth rate in other contexts
While this is true in some (limited) circumstances, the weight of demographic evidence is that rising incomes do on average (
ceteris parabis) reduce births. The issue isn't with the relationship between income and births per say but with how those factors interact within populations. Basically, some populations for various reasons tend to be more sensitive to income effects while others tend to be less sensitive. These reasons include: decisions about when to marry, female participation rates, education and so forth.
Dachs said:
while the latter is barely a necessary condition, and certainly not a sufficient one.
It depends on what birth control includes. If there are two populations and one marries earlier while the other marries later
ceteris parabis the former will tend to have a lower birth rate. If only because women who marry later are fertile for shorter periods of time. At least in a demographic sense delayed marriage is usually considered a form of birth control, albeit not a 'technical' kind. That's at least one example of non-technical birth control, there are others.
=Dachs said:
And that's ignoring whether these claims are even true, which is debatable as far as I know.
At least in studies of contemporary populations, it is true. I would tend to lean towards it not being as applicable in a context where income growth was rather slower than in contemporary developing nations where this effect is still playing out. (Most developed countries seem to have plateaued over the last couple of decades, so there does seem to be an upper limit to our willingness not to have children). Having said that, birth rates didn't suddenly collapse in Europe but tended to fall slowly over time, unlike a lot of developing countries where there have often been
huge declines in relatively short (demographically speaking) periods. (The Cambodian bump is due to the fall of the Khmer Rogue allowing people to begin having children again and a significant reduction in maternal deaths as the health system improved. Vietnam had a similar bump after the Vietnam War ended).
Owen Glyndwr said:
France has not had replacement reproduction numbers for much of the 20th century. Germany, by contrast has.
If France's replacement rate was below 2.1, its population should have fallen unless it covering the 'gap' in natural increase out of immigration. I kind of, sorta, doubt it was doing that in the early parts of the 20th century, at least.
I'm also dubious about talking about replacement rates... in the context of say the 1900s. The data probably isn't good enough to calculate them with any degree of modern precision. Keep in mind that even small differences in replacement rates are demographically significant. One can talk about growth rates because the kinds of things that drive under-reporting of births/deaths/marriages tend to be relatively constant over time or at least rather more constant than changes in the levels of under-reporting.
