Hampton Gaddy
@hggaddy.bsky.social
Demographer | PhD student, @lseechist.bsky.social | Usually working on the 1918 flu | he/him | https://hggaddy.github.io/
If you want a cool throwback to some really old school demography, Etienne van de Walle (1968) made a very similar point to us (pics attached but let me know if you want the PDF, it's hard to find). Goldman & Pebley is another classic source here (OA link: publishing.cdlib.org/ucpressebook...) (2/3)
October 21, 2025 at 10:08 PM
If you want a cool throwback to some really old school demography, Etienne van de Walle (1968) made a very similar point to us (pics attached but let me know if you want the PDF, it's hard to find). Goldman & Pebley is another classic source here (OA link: publishing.cdlib.org/ucpressebook...) (2/3)
But reality is more complicated! Sex-selective abortion is abhorrent, but its marriage market impact isn't large. Taiwan and Japan have ~4x higher rates of unmarried men than China, because the social pressure to marry in China is broadly higher (12/14)
www.demographic-research.org/articles/vol...
www.demographic-research.org/articles/vol...
October 6, 2025 at 12:45 PM
But reality is more complicated! Sex-selective abortion is abhorrent, but its marriage market impact isn't large. Taiwan and Japan have ~4x higher rates of unmarried men than China, because the social pressure to marry in China is broadly higher (12/14)
www.demographic-research.org/articles/vol...
www.demographic-research.org/articles/vol...
So what's the story here? High-polygamy communities like rural West Africa (and Utah in 1880) have strong pro-marriage norms. Polygamy reduces men's ability to marry in theory, but these norms seem to override that effect, meaning that men marry more in places with polygamy, not less! (10/14)
October 6, 2025 at 12:45 PM
So what's the story here? High-polygamy communities like rural West Africa (and Utah in 1880) have strong pro-marriage norms. Polygamy reduces men's ability to marry in theory, but these norms seem to override that effect, meaning that men marry more in places with polygamy, not less! (10/14)
Data from the US in 1880 show the same pattern. Counties with Mormon polygamy usually have lower rates of young men who've never married, especially vs. other counties in the West. And this holds even after controlling for sex ratios: it's not just that polygamy happens in feminine places (9/14)
October 6, 2025 at 12:45 PM
Data from the US in 1880 show the same pattern. Counties with Mormon polygamy usually have lower rates of young men who've never married, especially vs. other counties in the West. And this holds even after controlling for sex ratios: it's not just that polygamy happens in feminine places (9/14)
The global census data show that, within countries, communities with more polygamy usually have *fewer* unmarried men! This is the pattern in 50% of countries, while in another 43% there is no relationship. Polygamy being associated with unmarried men is the exception, not the rule (8/14)
October 6, 2025 at 12:45 PM
The global census data show that, within countries, communities with more polygamy usually have *fewer* unmarried men! This is the pattern in 50% of countries, while in another 43% there is no relationship. Polygamy being associated with unmarried men is the exception, not the rule (8/14)
Then we look at the real world using census data from @ipums.bsky.social. Our data covers 30 countries in Africa, Asia, and Oceania that practice polygamy, plus historical data from the 1880 census of the US, allowing us to look at Utah in the era of Mormon polygamy (7/14)
October 6, 2025 at 12:45 PM
Then we look at the real world using census data from @ipums.bsky.social. Our data covers 30 countries in Africa, Asia, and Oceania that practice polygamy, plus historical data from the 1880 census of the US, allowing us to look at Utah in the era of Mormon polygamy (7/14)
To start with, we show the number of men and women in a marriage market usually isn't equal. At the extreme, when mortality is high, women outlive men, men marry younger women, and the population is growing, 50% of men can marry 2.5 women each, "leaving" 1 wife for the other 50% of men (6/14)
October 6, 2025 at 12:45 PM
To start with, we show the number of men and women in a marriage market usually isn't equal. At the extreme, when mortality is high, women outlive men, men marry younger women, and the population is growing, 50% of men can marry 2.5 women each, "leaving" 1 wife for the other 50% of men (6/14)
LSE and @bspsuk.bsky.social are hosting a workshop on "Being an academic in population studies" on 3 November! It'll be a nice mix of methods training and career advice with great talks by @ericbschneider.bsky.social, Wendy Sigle, José Manuel Aburto, and others!
www.eventbrite.co.uk/e/being-an-a...
www.eventbrite.co.uk/e/being-an-a...
September 26, 2025 at 11:29 AM
LSE and @bspsuk.bsky.social are hosting a workshop on "Being an academic in population studies" on 3 November! It'll be a nice mix of methods training and career advice with great talks by @ericbschneider.bsky.social, Wendy Sigle, José Manuel Aburto, and others!
www.eventbrite.co.uk/e/being-an-a...
www.eventbrite.co.uk/e/being-an-a...
Ugh, I regret to discover that this plot is actually in the supplement of his Nature Reviews Endocrinology article. The inaccurate, fearmongering "levels of unsustainable fertility rates and population sizes" figure is also in the main text
www.nature.com/articles/s41...
www.nature.com/articles/s41...
August 16, 2025 at 9:20 AM
Ugh, I regret to discover that this plot is actually in the supplement of his Nature Reviews Endocrinology article. The inaccurate, fearmongering "levels of unsustainable fertility rates and population sizes" figure is also in the main text
www.nature.com/articles/s41...
www.nature.com/articles/s41...
A student yesterday: "Not even ChatGPT understands Lexis diagrams..." I guess the spatial logic of triangles, squares, and parallelograms trips it up? I just asked it to explain and draw a Lexis parallelogram, and yeah, it didn't go great. Maybe a tip for testing demographic reasoning these days!
May 15, 2025 at 9:46 AM
A student yesterday: "Not even ChatGPT understands Lexis diagrams..." I guess the spatial logic of triangles, squares, and parallelograms trips it up? I just asked it to explain and draw a Lexis parallelogram, and yeah, it didn't go great. Maybe a tip for testing demographic reasoning these days!
Maybe helpful: the famous Myrskyla association faded pretty quickly after the global financial crisis! And, if you use a more available metric of development (HLI), by the late 2010s, you could find all levels of 1.2 - 2.0 TFR at all high levels of HLI
www.demographic-research.org/Volumes/Vol4...
www.demographic-research.org/Volumes/Vol4...
May 11, 2025 at 4:38 PM
Maybe helpful: the famous Myrskyla association faded pretty quickly after the global financial crisis! And, if you use a more available metric of development (HLI), by the late 2010s, you could find all levels of 1.2 - 2.0 TFR at all high levels of HLI
www.demographic-research.org/Volumes/Vol4...
www.demographic-research.org/Volumes/Vol4...
"Welcome to Leslie Root" One of the better emails I've gotten all day 😂
April 30, 2025 at 5:51 PM
"Welcome to Leslie Root" One of the better emails I've gotten all day 😂
Next Wednesday, 7 May, I'll give a Campop seminar on some of my recent excess mortality methods work! The focus is on historical epidemics, but I'll also touch on low-data settings and using excess mortality for inference in general. Let me know if you want the Teams link!
April 28, 2025 at 8:00 AM
Next Wednesday, 7 May, I'll give a Campop seminar on some of my recent excess mortality methods work! The focus is on historical epidemics, but I'll also touch on low-data settings and using excess mortality for inference in general. Let me know if you want the Teams link!
In our new paper, @thegargiulian.bsky.social and I argue that demographers can't be afraid to be qualitative. There are many historical and contemporary crises where the most objectively accurate information available is qualitative, not quantitative
www.demographic-research.org/articles/vol...
www.demographic-research.org/articles/vol...
April 10, 2025 at 12:51 PM
In our new paper, @thegargiulian.bsky.social and I argue that demographers can't be afraid to be qualitative. There are many historical and contemporary crises where the most objectively accurate information available is qualitative, not quantitative
www.demographic-research.org/articles/vol...
www.demographic-research.org/articles/vol...
One takeaway is that we don't always need numbers. GRDM gave us the only half-decent death toll estimate for the Cherokee Trail of Tears (Thornton 1984), but that estimate has huge uncertainty. Yet, we still qualitatively understand this event well, including that it was ethnic cleansing (8/9)
April 10, 2025 at 12:07 PM
One takeaway is that we don't always need numbers. GRDM gave us the only half-decent death toll estimate for the Cherokee Trail of Tears (Thornton 1984), but that estimate has huge uncertainty. Yet, we still qualitatively understand this event well, including that it was ethnic cleansing (8/9)
This method also appears in econometric work on the effects of Partition and the roots of the 1960s killings in Java. But GRDM results are terrible proxies for well-validated subnational death toll estimates and are confounded by endogenous factors like state capacity and pre-crisis demography (7/9)
April 10, 2025 at 12:07 PM
This method also appears in econometric work on the effects of Partition and the roots of the 1960s killings in Java. But GRDM results are terrible proxies for well-validated subnational death toll estimates and are confounded by endogenous factors like state capacity and pre-crisis demography (7/9)
We wish this method worked—it would help with our own research! But since it doesn't, existing GRDM research should be revisited: from the Black Death, to the Taiping Rebellion and 1918 flu. Popular stats for the world's deadliest war and earthquake both come from this unreliable method (6/9)
April 10, 2025 at 12:07 PM
We wish this method worked—it would help with our own research! But since it doesn't, existing GRDM research should be revisited: from the Black Death, to the Taiping Rebellion and 1918 flu. Popular stats for the world's deadliest war and earthquake both come from this unreliable method (6/9)
When researchers have used GRDM and then used a better demographic method, it's clear that GRDM has a highly inaccurate track record. It routinely under- or overestimates death tolls by 2, 3, or 4x! This is an amount of (im)precision that is rarely useful (5/9)
April 10, 2025 at 12:07 PM
When researchers have used GRDM and then used a better demographic method, it's clear that GRDM has a highly inaccurate track record. It routinely under- or overestimates death tolls by 2, 3, or 4x! This is an amount of (im)precision that is rarely useful (5/9)
However, GRDM's outputs are extremely uncertain. Almost all published versions of the method don't include sensitivity checks. But small cumulative amounts of uncertainty in GRDM's inputs can lead you to estimate a death toll for the 1918 flu in British India anywhere between 0 and 39 million! (3/9)
April 10, 2025 at 12:07 PM
However, GRDM's outputs are extremely uncertain. Almost all published versions of the method don't include sensitivity checks. But small cumulative amounts of uncertainty in GRDM's inputs can lead you to estimate a death toll for the 1918 flu in British India anywhere between 0 and 39 million! (3/9)
There are many different ad hoc methods that work like this, but no one has reviewed them or given them a name! @thegargiulian.bsky.social and I call them the growth rate discontinuity method (GRDM), and they appear all over the history of mortality crises, from the 8th century to the 1990s (2/9)
April 10, 2025 at 12:07 PM
There are many different ad hoc methods that work like this, but no one has reviewed them or given them a name! @thegargiulian.bsky.social and I call them the growth rate discontinuity method (GRDM), and they appear all over the history of mortality crises, from the 8th century to the 1990s (2/9)
Polygyny has important context-dependent effects but the idea that it's an obvious reason for men being violent (in rural Africa, or among incels) doesn't hold up demographically. But this hasn't stopped The Economist and many researchers from saying that polygyny is to blame for everything (4/5)
April 1, 2025 at 3:50 PM
Polygyny has important context-dependent effects but the idea that it's an obvious reason for men being violent (in rural Africa, or among incels) doesn't hold up demographically. But this hasn't stopped The Economist and many researchers from saying that polygyny is to blame for everything (4/5)
Actually, social composition effects mean that, in ~50% polygynous countries, the places with the most polygyny have the least unmarried men! Another ~40% have no association, even after controlling for the local sex ratio. Communities that marry polygynously, usually marry more overall (3/5)
April 1, 2025 at 3:50 PM
Actually, social composition effects mean that, in ~50% polygynous countries, the places with the most polygyny have the least unmarried men! Another ~40% have no association, even after controlling for the local sex ratio. Communities that marry polygynously, usually marry more overall (3/5)
The idea that a polygynous marriage prevents another man from marrying at all, or that polygyny means "perhaps even 50% of men have no descendants" is intuitive, but polygyny's effect here depends on a dozen other variables. And they often allow for pretty high rates of "sustainable" polygyny (2/5)
April 1, 2025 at 3:50 PM
The idea that a polygynous marriage prevents another man from marrying at all, or that polygyny means "perhaps even 50% of men have no descendants" is intuitive, but polygyny's effect here depends on a dozen other variables. And they often allow for pretty high rates of "sustainable" polygyny (2/5)
Since polygyny is back in the news today, a reminder that the huge political science literature linking polygyny to civil war and male aggression is based on faulty demographic assumptions about how polygynous marriage markets work! 🧵
April 1, 2025 at 3:50 PM
Since polygyny is back in the news today, a reminder that the huge political science literature linking polygyny to civil war and male aggression is based on faulty demographic assumptions about how polygynous marriage markets work! 🧵
Have we ruled out that higher / worse Covid burdens aren't a decent part of the story? I'm not sure the magnitude makes sense, but the age-standardised Covid death rates were at least 2x those in some of the comparison countries (doi.org/10.1111/padr...)
March 12, 2025 at 2:58 PM
Have we ruled out that higher / worse Covid burdens aren't a decent part of the story? I'm not sure the magnitude makes sense, but the age-standardised Covid death rates were at least 2x those in some of the comparison countries (doi.org/10.1111/padr...)