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Population decline
salamandraugr wrote in little_details
Setting: Secondary world technologically equivalent to the early 19th century.
Search terms: no new births, declining birth rate, sub-replacement fertility, historical pregnancy per capita, historical birth rate

My story takes place in a city of roughly 1.5 million people. A little over half of these people are natives of the country. The rest are immigrants ranging from first generation to people whose ancestors came over centuries ago. The newest ethnic group to arrive in the city - the Mirevans - is about 32,000 people strong. The Mirevans only started immigrating about 20 years ago as a result of a civil war in their homeland of Mireva.

What's a realistic number of pregnant women among these 32,000 people? How much chaos would it cause in the city if every pregnant Mirevan woman - regardless of what stage of pregnancy she was in - stopped being pregnant overnight as a result of weaponized magic? About a fifth of these women also die. Of those that live, maybe one in ten is rendered infertile.

It's discovered later on that the same thing has happened in Mireva, which has a population of about 2.5 million people. How badly would this disrupt their society? How much would the population of Mireva decrease over the next year or so given that there are no new births to replace the people who die each day? In addition to natural deaths, they also have to deal with an ongoing border war that kills off a few thousand conscripts a year, which would of course reduce the number of men available for marriage/procreation. The Mirevan faith doesn't allow polygamy or the marrying of people who aren't Mirevan so that would have to hurt population numbers as well.

Modern statistics help a little, but the better healthcare available today - at least in the developed world - also means longer life expectancies, less deaths in childbirth, and a lower infant mortality rate. Magic exists but there is no healing magic. Also the world is well into the age of quackery. Patent medicines - some of them lethal, many of them worthless - are sold on every corner and by pretty much every "reputable" alchemist/apothecary.

Some of it's going to depend on other factors. You could roughly estimate maybe 15-20% of a pre-modern population are women of childbearing age (many children, few old people) but an immigrant population is probably going to have a larger number of people who were older children and young adults at time of immigration and who are able to travel, so skew that a bit higher to say 25%. Of all women, there's a steady number of about 12.5% (up to 30% in certain times and places) who never have children, so let's knock that back to 15-20%.

Of these women, you could have up to 50% pregnant at any given time (one pregnancy a year), depending on lifestyle, diet, breastfeeding practices etc. Women with less food and/or longer breastfeeding times are going to have children less frequently, and if there's a major female religious tradition involving celibacy, or later marriage, that will affect the numbers too.

Let's say the women have sufficient food, no reliable contraception, sufficient available men and tend to breastfeed their own children. That would mean a maximum of about 2400 pregnant women at any given time out of your population of 32000.

ETA: I don't think one year without children born is going to have much of an effect on your population overall, but remember than most of those women who die will leave behind children and someone will have to care for them. Kinship care systems will be well-developed but that's a massive strain all in one hit.

Edited at 2014-02-24 05:12 am (UTC)

I think the reduced number of women is likely to have more effect than one year with no babies.

The first world war killed roughly 2% of the British population and had a significant effect on the ability of women to find husbands in the years following.

If 10% of your population are pregnant at the time of the event and 1-in-5 of them die that's 2% of your population dead (2400 is a bit less than 10%). Worth considering that if all the men have gone orf to fight a war then they aren't at home getting their wives pregnant.

I would expect that most of the war dead would be male; so the problem of a gender imbalance might be reduced.

Having this event happen may make women more worried about pregnancy than before (although pregnancy is already pretty worrying if you don't have good health care) - is it possible it will happen again? Although reliable contraception is unlikely to exist *unreliable* contraception probably does, and is widely known about, possibly disapproved of but likely used; abstinence of course does work... will a year of no babies lead women to try harder to have babies, or to try harder to avoid babies?

I like those numbers. 2400 women losing their babies and over 400 of them dying in a single night would be enough to scare the rest of the city, even those of other ethnic groups. Word of mouth and yellow journalism would make things seem significantly worse.

Dunno how deep you want to go for background, but if you're interested in public reaction in Britain to this event, Malthus was writing about related issues in early 19th Century.

These are links at

An Essay on the Principle of Population

1798: An Essay on the Principle of Population, as it affects the future improvement of society with remarks on the speculations of Mr. Godwin, M. Condorcet, and other writers.. Anonymously published.

1803: Second and much enlarged edition: An Essay on the Principle of Population; or, a view of its past and present effects on human happiness; with an enquiry into our prospects respecting the future removal or mitigation of the evils which it occasions. Authorship acknowledged.
8 Other works
8.1 1800: The present high price of provisions
8.2 1814: Observations on the effects of the Corn Laws
8.3 1820: Principles of political economy

For names people might be dropping at that time, see:
[ In an earlier debate ] Malthus had a supporter in William Blake, in denying that capital accumulation (saving) was always good in such circumstances, and John Stuart Mill attacked Blake on the fringes of the debate.[26]

Thanks. I'll take a look at the text.

What's a realistic number of pregnant women among these 32,000 people?

If the population is neither growing nor shrinking because of birth and death (excluding immigration), then each female has enough children over the course of her childbearing years to keep the population stable, no more and no fewer. In a modern western society, that number (the replacement fertility rate) is around 2.1 children per woman. If we estimate a woman's childbearing years as 20-35, then she has 16 years to produce those 2.1 children. Gestation takes nine months, so that sixteen years works neatly out to about 21 gestational periods. Ten percent of the women should be pregnant at any one time. That's 1600 pregnant women from the population of 32000.

Replacement rates will be higher in less-developed countries, of course, as more people die before reproducing.