Her second post is called “You’ll probably die alone”, and includes the following statement:

“If you were born in 1960, over three quarters of your peers would be married by 30. Only about 15% of people should expect to be terminally unwed.

This is the world of Sex and the City and Friends and it’s totally lost to us.”

This is false. While timing of marriage has shifted later, there is no lost world of marriage for the American upper-middle class.

Educated American women are as likely to be married as their counterparts 40 years ago.

(from Scarcity of College Men and the Decline in Marriage Among Non-College Americans)

This bears some emphasis. Marriage rates for college-educated women have been flat since the cohort born in the 1940s. There is no lost world of marriage.

Note that this graph does include recent cohorts; this includes those who turned 45 in 2025.

It does not include most Millennials or Gen Z, because it is not yet possible to determine if they will be married by 45. Given the stability of this number over time, though, I’d be surprised if Millennial women suddenly decided marriage was Not For Them.

Indeed, marriage has become increasingly class-linked in the United States. Consider the following graph of the percentage of women that are married by income:

(from Marry for Money or Time? Explaining New Marriage Trends in the U.S.)

The likelihood of a woman in the top income quartile - an income of around $85k for a 30 year old in the US2 - being married3 has increased over time. If you’re an elite woman, your prospects for a successful marriage may be better than they were 25 years ago.

You’ll probably only spend a couple fewer years married than your forbears - and they’ll probably be happier ones

There is also a broader point to be made about all of these essays, even if you are not a highly educated elite. In general, most people’s goal for marriage is not marriage per se, it is a successful marriage - that is, one ideally not ending in divorce.4

Therefore, I think it is reasonable to compare the amount of your life spent married rather than one’s relative success at getting to the altar. There are several demographic changes that affect the expected number of years married besides marriage rates. At the same time that marriage rates have fallen, divorce rates have also fallen; life expectancy has increased.5

Let us compare two women: one born 1958, one born 1998. The first was born during the Baby Boom, the prototypical high-marriage-rate environment. The second is a member of Gen Z, a generation supposedly uninterested in marriage.

On average, the woman born in 1958 is more likely to marry (90% would eventually marry), and when she does marry, she marries earlier (age 22). But Gen Z marriages are much more stable - divorce rates for first marriages have declined from ~45% to ~30%.6

I calculate out the expected number of years each will spend married in the appendix, and find that the Baby Boomer would (on average) be married 33 years of her life. The Gen Z woman? About 30 years of her life.

Three fewer years of marriage is a decline, to be sure, but “a disaster, the likes of which our civilisation has never seen” feels more than a bit overdramatic. (It also seems entirely possible that relationship-years are similar, since engagements tend to be longer; few people now marry after being together six or eight months.7)

The story for college-educated women is even more positive. More college-educated women marry8 and fewer divorce. Given that college-educated women are just as likely to be married at 45 as they were for previous cohorts, and are less likely to divorce, it is entirely possible that they will spend more of their lives married.

Even including the non-college-educated, though, a 28-year-old woman today will spend just as much time married as one born in 1958. She is also considerably less likely to go through the messy, painful, expensive process of getting a divorce.

Spinsterhood As A Great Western Tradition

Someone, I’m sure, is going to point out that 70% of Gen Z college women marrying is not 100%. This is true. But 70% is… not that abnormal for a Western country. The US and the UK have never had universal marriage, especially for educated women.

In the US, the percentage of white women never married in the age range 45-54 has varied from around 4% (the Baby Boom) to around 10% (those born around 1870). Now, 17% of women have never married by 45, with rates of spinsterhood (unmarried by ~45) for college-educated women around 13%. This is an increase, certainly, but a catastrophic collapse of marriage it is not.

Historical spinsterhood rates in the UK were higher; in Tudor England, the likelihood of remaining unmarried for your entire life was about 20%. By the Victorian era, spinsterhood rates exceeded 30% in some parts of the UK. Now, about 36% of women in the UK have never married by 45. Again, this is an increase, but there is no vanished world of marriage.

Historically, marriage rates for the educated were especially low9 - only 56% of the first ten classes at Vassar married. Only 72% of the Harvard men of the classes 1867-76 married. If about three-quarters of your highly educated, elite social circle is married by 46, you are… historically pretty normal.

Lack Of A Marriage Is Not A Lack of A Relationship

You may note that all of my marriage rate data is from the US. The US is a more marrying place than the UK, likely because it is also more religious.

In the UK, cohabitation replaces some percentage of relationships that would likely be marriages in the US. I think roughly 70% of Gen Z will marry in the US; in the UK, it is likely to be closer to 50%.10 In societies like this, though, the relationship decline is considerably smaller than the marriage decline.

Currently, about 25% of non-married adults in the UK are in such non-marital but cohabiting relationships.11 Many of these will eventually become marriages, but not all will; long-term cohabitation has become more common as an alternative to marriage rather than a prelude to it.

So: those 30% of never-marrieds in the US (and perhaps 40-50% never-married in the UK)? They won’t necessarily die alone. And if what you want is the right partner to make achieving your other goals easier, cohabitation clearly counts. Cohabiting couples have many of the benefits of marriage.12

So while it is true that the UK cohort born in 1970 will see 20% fewer of its members marry than the 1940 cohort, it does not mean that those 20% will be single for the rest of their lives.13

Indeed, the total fraction of people in committed couples has been relatively stable over the last decade and a half. In the 2011 census, 57.8% of the population in England and Wales was living in a couple. The 2021 census found almost exactly the same percentage of the population living as a couple - even as marriage rates continued to decline.

Marriage, then, is not the whole story. Particularly in the UK, cohabitation without marriage is common enough that “never married” does not mean “forever alone”.

Conclusion

The data shows no collapse in relationship formation among the demographics most likely to worry about a collapse in relationship formation. Indeed, a woman today will spend about as much time married as a woman born during the Baby Boom, and she’s quite a bit less likely to get divorced.

Is it true that “a lot of beautiful and interesting women… are going to end up single”? Sure. But for the college-educated, that’s no more likely now than it was in the past - even if you don’t count the uptick of non-marital long-term relationships.

As it turns out, our settling down technology is working just fine.

Many thanks to and for reading drafts of this, and for telling me to banish the math to an appendix.

Appendix

We assume that a woman born in 1958 has a life expectancy at birth of 73, and a woman born in 1998 79.14 The two women can have the following outcomes:

• Never married

• Married once (until death)

• Married once and divorced; do not remarry

• Married twice; the second marriage lasts until death

• Married twice and divorced both times

For the sake of the model, I am choosing to ignore third or more marriages.15

For women born 1958, the likelihood of each category breaks down as follows:

• Never married - about 10%

• Married once (until death) - about 50%16

• Married once and divorced; do not remarry - about 16%17

• Married twice; the second marriage lasts until death - about 8%18

• Married twice and divorced both times - 16%19

Calculating the length of each of these - and thus, the average marriage-years - is slightly trickier. We assume that a woman born 1958 has an average life expectancy of 73.

• Never married - 0 marriage-years

• Married once (until death) - married from age 22 to 73;20 51 marriage years

• Married once and divorced; do not remarry - married about eight years;21 8 marriage-years

• Married twice; the second marriage lasts until death - married for eight years in first marriage; four year gap between marriages; second marriage starts age 34 and ends at 73 and thus lasts 39 years; contributes a total of 47 marriage-years

• Married twice and divorced both times - first marriage is eight years; second is seven; 15 marriage years

Therefore, the average number of marriage-years for a woman born 1958 is 33.22

Let’s consider a woman born 1998, marrying in 2026, at age 28.

We also know that the risk of divorce per year of marriage is now about two-thirds what it was in the 1980s. We know that about 45% of first marriages in the 1980s ended in divorce; therefore, I estimate that 30% of modern first marriages will end in divorce.23

Our categories are:

• Never married - perhaps 30%

• Married once (until death) - about 49%24

• Married once and divorced; do not remarry - about 8%25

• Married twice; the second marriage lasts until death - about 7%26

• Married twice and divorced both times - about 6%

The expected marriage-years for each category are:

• Never married - 0 marriage-years27

• Married once (until death) - married from 28 to 79; 51 marriage-years. Note that this is the same number of expected marriage-years for the 1958 cohort, even though marriage is later; life expectancy gains completely offset this.

• Married once and divorced; do not remarry - as above, eight marriage-years

• Married twice; the second marriage lasts until death - eight marriage-years from first marriage; second marriage with similar divorce/remarriage timing will now occur at age 40, meaning the second marriage now lasts 39 years. Total of 47 marriage-years.

• Married twice and divorced both times - fifteen marriage years

This woman’s expected marriage-years is therefore 30.28

So for all women, the number of years of marriage has declined about three years, or about 4% of her lifetime.

Are the poorest people in the world scratching out a living farming in rural India, or working long hours in a factory in China?  Are they living in slums in Jakarta or Delhi?

Increasingly, the world’s poorest people are not in any of these places.  That is not to say that there is not poverty there; about half of the world’s poorest people still live in stable-but-growing states.  But as time goes on, the world’s poorest - those who live below the World Bank’s extreme poverty line of $2.15 a day - are increasingly concentrated not in stable countries, but in unstable ones.

The below chart shows that while the number of people in poverty in stable states - labeled as “other” - has declined sharply, the number of people in poverty in fragile states - labeled as “FCAS (fragile and conflict-affected)” states - hasn’t:

(from CGD)

Right now, there are still more people in extreme poverty in stable states than in fragile ones, but this will soon change.

There is a pretty clear reason for this.  Life is getting better in most poor countries.  Progress is slow, and there is still a long way to go, but most people in low income countries will have a better life than their parents did, and their children will have a better life than they did.  In India and China and Indonesia and Kenya and Tanzania, the number of people living in extreme poverty is decreasing over time.

This is not true in fragile states.  Fragile states are states with weak state capacity, where the government is not perceived as legitimate, or where there is ongoing civil conflict.  This includes places like Yemen, Afghanistan, and Somalia - but also Nigeria, Lebanon and Venezuela.  In some of these places, the state is virtually nonexistent; in others, there is still some state providing public goods, but not a lot.

It is perhaps not a surprise that these countries have not seen the growth that more stable states have seen.  It is easier to set up a business in Kenya than in Somalia; easier to work in EU-member Croatia than still-fragile Kosovo.  But what is particularly striking is how much of a difference there is between fragile and stable states.  Across a variety of indicators, things are getting better in stable states; there is not much evidence that things are getting better in fragile states. For instance, child mortality shows the same pattern:

(from CGD; again, FCAS = fragile and conflict-affected states; other = stable states)

This means that anyone interested in reducing extreme poverty must work on and in fragile states.  The problem is that nothing really works in fragile states.

That’s basically the definition of a fragile state - the government is unable to provide services, and the population is skeptical of the government’s legitimacy (and their need to pay taxes).  Contracts are suggestions, and in some fragile states, may be renegotiated at gunpoint.

It is famously difficult to operate in fragile and weak states.  Let’s say, for instance, you run an NGO trying to distribute bednets.  You need to procure some bednets, and get them to the people who need them.  In a stable but poor state, this isn’t easy - the road quality in rural Uganda isn’t great, and driving can be a bit of an adventure - but it is possible.

In the DRC?  Well, your first duty as an employer is to make sure that none of your employees get killed.  What if they’re held up by bandits?  Should your team carry cash, to pay off corrupt cops at roadblocks, or should they not, so they’re not a target for robberies?  What if there’s a medical emergency?  Where is the nearest hospital, anyway?  Do they have power?  The one paved road that you were planning to take was washed out in a flash flood; what’s the chance that your alternate route will be passable?  It’s all the normal difficulties of operating in a poor country, plus several thousand more.

And this doesn’t just hold for NGOs.  Generally, countries get out of poverty slowly, as more people move from the informal sector to the formal sector and incomes rise.  It’s a very slow process, but over time: more people stay healthy for longer; more people go to school, more people get jobs in services or manufacturing instead of agriculture.

All of that progress can be undone very quickly.  Fundamentally, you need peace and security for growth.

It’s not safe for your child to get to school because there’s a rebel group operating the area?  Well, clearly they’re not going to go to school; their life matters more than attending school.  The community health worker can’t make it to your village because the non-functional government hasn’t paid their salary in six months?  Guess your kid isn’t getting treatment for malaria.  That company that was going to open up a store in your village ended up backing out because it’s just too risky without a legal system that works?  Well, you can always continue to farm.  Every one of the thousands of baby steps needed for economic development can be derailed by state fragility and conflict.  

Displacement is also very disruptive.  People - very reasonably - do not want to become the next casualty in a war, and about 30 people will flee their homes for every conflict death.  As they flee, though, services - both medical and commercial - are disrupted.

The worst consequences are medical.  The people fleeing may be the doctors and nurses and community health workers that are needed to keep the community healthy, and there is a distinct lack of continuity of care while fleeing across the country or across borders.  Most of the deaths in civil conflict don’t occur on the battlefield; they are caused by disrupted medical care rather than shrapnel wounds.

The monetary cost of disruption is minor by comparison, but is still significant.  Some of the people who flee will be business owners.  Shopkeepers can’t take their stores with them, farmers cannot take their crops.  Though figures vary, a conflict can reasonably be assumed to decrease GDP/capita growth 5% a year.  Since low or middle income countries grow at about 4% per year (on average), this means that as long as there is conflict, there will be no growth.

And without growth, extreme poverty will not decline.  Reducing conflict is not sufficient for structural transformation, but it seems to be necessary.

The Case for Peacekeeping

So… what do we do about this?  Prevent civil conflict and strengthen weak states?  Yeah, that sounds super easy; I’ll get right on that.  But there is a solution that has been shown to work: UN peacekeeping.

No, really.  UN peacekeepers are widely perceived to be ineffective, blue-helmeted buffoons that wander around war zones being vaguely useless.  They are rarely allowed to actually fire their guns. They just stand around looking official.  They’re more like hall monitors than soldiers. 

But peacekeeping - no matter how useless individual peacekeepers seem - has been shown to work.  The academic literature is very clear on this:

• Walter 2002 finds that if a third party is willing to enforce a signed agreement, warring parties are much more likely to make a bargain (5% vs. 50%) and the settlement is much more likely to hold (0.4% vs. 20%).  20% is not an amazing probability for sustained peace, but it sure beats 0.5%.

• Page Fortna’s work shows that use of peacekeepers in a conflict reduced the likelihood of further war by 75%.

• Hegre et al 2019 finds that increased deployment of peacekeepers could have reduced conflict by two-thirds in 2001-2013.

• Blair 2020 finds that if peace is achieved, peacekeeping helps rebuild the rule of law in states where there is little rule of law to be found.

It turns out hall monitors are a thing that you need in a conflict.  Ceasefires largely happen when neither side believes they can win; ceasefires fail when one of the two sides believes that they now have the advantage and would win if they return to war.

Often, one side uses the peace of the ceasefire to quietly rebuild its fighting strength, retrain and re-arm.  This is usually against the terms of the peace agreement, but as long as the other side doesn’t know about it, you can get away with it.  Getting away with re-arming is much harder, though, when there are blue-helmeted hall monitors wandering around.

It is true that individual peacekeepers can do very little about violations of a ceasefire.  But they can call their boss, who calls their boss, and eventually the news reaches the UN security council, and then the US president is on the phone with the rebel leader asking why they violated the terms of the truce.  Peacekeepers provide law by bringing the mandate of the UN with them; they can truly be a neutral third party.

None of that means that peacekeeping is a panacea.

Even though peacekeeping helps, it isn’t a guarantee of peace.  After all, the longest running UN peacekeeping mission is trying to keep the peace between Israel and Palestine; it would be difficult to say its 76 year history has been a resounding success.  Peacekeeping in Sudan, South Sudan, the Democratic Republic of Congo?  It’s not clear those countries are better off than they would have been without peacekeepers.  Peacekeeping gives you a chance at a sustained peace, but that’s all it is - a chance.

UN peacekeepers are also not precisely who I would choose to have teaching the rule of law.  The UN only pays countries $1500 per soldier per month, so peacekeepers are often from countries where rule of law is limited to begin with.  Sexual abuse by peacekeepers has been widespread enough to require a Wikipedia article.

But even with all of those caveats: peacekeeping is still probably the best solution that we have for fragile states.  There are a few interventions that seem promising at reducing interpersonal violence at small scale (cognitive behavioral therapy, alternative dispute resolution) but we have little evidence on how they would work when scaled to a whole country.  Peacekeeping is one of the few things that we do have strong evidence on.  Peacekeeping works to reduce the risk of recurrent civil war.

And yet we aren’t using it all that much.  The UN Security Council seems to believe the endless articles about how useless peacekeepers are, and doesn’t seem all that enthusiastic about sending peacekeepers to new conflicts.  Since 2010, the number of deployed peacekeepers has been largely flat, even as conflict deaths have increased:

(Chart from Our World in Data)

This is suboptimal.  If the UN really is an organization dedicated to “maintaining international peace and security” and “promoting the well-being of peoples of the world”, peacekeeping is one of the best tools they have to support this mission.  The UN may be bloated, bureaucratic and slow-moving, but this is something they do that definitely works.

But it is not just bleeding-heart humanitarians of the UN who should care about peace and peacekeeping.  Anyone who cares about global poverty must also care about peace.  Without stabilizing fragile states, all our progress at reducing global poverty will soon stall out, leaving hundreds of millions living on less than $2 a day.

Peace allows countries at least the prospect of growth.  It is not a guarantee - growth is not always easy, even for countries at peace - but when there’s a civil war, it’s virtually impossible for a country to grow.  For poverty to decrease, to health to improve, for life to get better, for countries to grow - there must be peace.

And if you care about peace, you should probably also care about peacekeeping.

Many thanks to Denise Melchin, Rob L'Heureux, Steve Newman, Kevin Kohler and Jeff Fong for comments and edits on this piece.

Mostly, I think about it while sitting in an optometrist’s office, about to exchange a large amount of money for the ability to see for another couple of years.  But what if I couldn’t exchange money for the ability to see?

The State Of Global Vision Care

According to the WHO, only about half of the people with vision issues around the world are appropriately treated.  Some 800 million people need glasses and will not get them - a full 10% of the world population!

And the burden of untreated eye health issues is extremely unequal.  Most people with poor vision in rich countries will receive treatment; most people in poor countries will not; 90% of the people with untreated eye issues live in low and middle income countries.

Perhaps this isn’t all that surprising.  When healthcare is hard to access, eye care is even harder to access.  National health care systems often consider vision separate from other kinds of health, so vision is rarely incorporated into national plans.

Relatively few people have regular eye exams, because optometrists are rare outside of rich countries.  On average, a high income country like the US has 78 times as many optometrists per 100,000 population than a country in sub-Saharan Africa.

Furthermore, most people in low income countries live in rural areas, far from the nearest optometrist or optical store.  The most common type of medical provider is a community health worker (CHW).  A CHW is generally someone without a medical degree, but with some medical training.  A CHW who makes it to a village in rural Kenya will ask about malaria, about diarrhea, about pregnancy and childbirth - but vision is simply not in their remit.

But eye care really is essential, perhaps as essential as some of those services.  Vision problems are very common; some 25% of the entire population has some kind of vision issue.

Indeed, if you live long enough, you are essentially guaranteed to develop vision issues.  Developing presbyopia (farsightedness) is considered just a normal part of aging, because the lens in your eye becomes less flexible with age.  There is no way to prevent it; if you are still alive at age 50, you’re going to find reading things up close more difficult.  And indeed, some 500 million people worldwide have untreated presbyopia.  It is the most common form of vision issue, considerably more common (on a global scale) than nearsightedness.1

Thankfully, presbyopia is very easy to treat by wearing reading glasses.  Unlike nearsightedness, where there’s a wide range of possible prescriptions and you probably do need to see a medical professional, you can determine what reading glasses are best for you by trying on a few with different prescriptions, and seeing what works best.  That’s why you don’t need to see a doctor to get reading glasses in most rich countries - you can go to the drug store, spend $10, and you’re set.

But if you live in rural Kenya and the nearest place that sells reading glasses is in Nairobi?  You may be out of luck.  You can take time away from your job and your family and travel hours (if not days) to Nairobi, spending a considerable portion of your monthly wage just to get there.  And then buying the glasses is yet another upfront cost; you have to hope that once you have them, the glasses will be worth it.  And maybe you don’t have the money and the time right now, so you live with it.

Sure, maybe you can’t see as clearly as you once did, but that’s just the way life is.

Are Glasses That Valuable?

It doesn’t have to be - and it shouldn’t be.  In recent years, two major randomized control trials distributed reading glasses in developing countries.  Both found extremely large impacts on productivity and income.

Assam

In 2017, a team affiliated with the charity VisionSpring distributed reading glasses to tea pickers workers over 40 in Assam.  Tea pickers are paid based on how quickly and accurately they can pick tea leaves off the plants.  With glasses, their productivity (and income) increased 21%.  Perhaps unsurprisingly, 95% of those who received glasses said they’d buy another pair if theirs ever broke.2

Bangladesh

Another study distributed glasses to people with presbyopia in Bangladesh.  These people worked in a variety of occupations - farming, weaving, selling food - but all reported they needed to look at things that were close up at least some of the time.3

Eight months later, the participants that received glasses had incomes 33.4% higher than those that did not.  The glasses more than paid for themselves; getting a $10 pair of glasses increased earnings by $11.80 every month.  If the glasses last a year, workers would expect to earn $141.60 more because of their $10 glasses.

These are very large income and productivity increases.  Going to school for another year only raises your income (on average) about 9%; simply using reading glasses raised incomes as much as if everyone had gone to school for three more years.  And reading glasses are definitely cheaper to provide than three more years of school.

Will We Fix The Vision Care Gap?

A few global development funders have taken notice.  GiveWell and the Livelihood Impact Fund have funded another trial distributing reading glasses, this time in India and Kenya.4  But they are the exception, not the rule.

The amount of funding addressing this massive global problem remains relatively small in comparison to the problem, though.  The unfilled need for reading glasses alone is something like $5B.  And one of the largest NGOs in the field, VisionSpring, took in just $20M last year.  Another NGO is targeting getting glasses to 250M million people in the next ten years - but so far, their budget only suffices to distribute fewer than 400,000 pairs a year.  At that rate, they will miss their target by an order of magnitude.

So what is to be done?  Well, funding so far has come from relatively small actors in the global development space.  Governments and aid agencies need to wake up the idea that vision matters to productivity.

Funding glasses distribution could be one of the highest impact things an aid agency does.  Most development interventions are considered “good buys” (for donors or governments) if they return $15 in social benefits for every $1 spent.  Every $1 spent on reading glasses could result in $46 more in earnings.  That’s not a good buy; that’s a best buy - maybe one of the best buys in global health.  More funders should make that buy.

Extra thank yous to Steve Newman, Denise Melchin, and Rob Tracinski, who reviewed this draft on short notice.

This is wrong.  Increasingly, air conditioning isn’t a luxury.  It is survival technology.

Life On A Warming Planet

The IPCC estimates that the earth has already warmed about one degree Celsius1 over the last century, and every year is hotter than the last.

We are already seeing the effects of this.  It’s harder to concentrate in the heat, harder to be productive, harder to sleep, harder to think straight.

This manifests in a variety of domains:

• For every degree the temperature rises, students learn less.  Already, about 90,000 New York high school students had to take an extra year in school because they took exams in non-air-conditioned conditions and did worse than they otherwise would.

• Workers are worse at their jobs too.  At 95 degrees, worker productivity is just two-thirds of what it would be at 70 degrees.  This already costs the US economy $100B a year, and is projected to rise to $500B a year by 2050.

• Some of that may be because everyone’s tired - humans sleep worse in the heat, spending more time in shallow sleep and less time in deep, restful sleep.

• Heat also makes people more irrational.  Homicides and suicides go up on hot days - some 7% of US homicides may be caused by the heat.

And people die.  Often, these deaths go unnoticed, because they don’t seem to be directly caused by the heat.  Nonetheless, they are; heat increases the stress on the heart and makes other causes of death (like strokes and heart attacks) more common.

In 2003, Europe - where just 19% of the population has air conditioning - had an extended heat wave.  70,000 people died.  This is not a small number - it’s comparable to the number of deaths in the worst weeks of the COVID-19 pandemic.  In 2010, 54,000 Russians perished during another heat wave - almost as many as have died in the war in Ukraine.

Another 60,000 Europeans died to excess heat in 2022, even as Europeans remain reluctant to install AC for climate reasons.2

Heat Waves in the Developing World

Elsewhere in the world, air conditioning is even rarer.  Consider India - where just 8% of households have air conditioning.  That’s concerning, considering India’s dangerous combination of heat and humidity.

The human body relies on evaporative cooling via sweating - but that requires that our sweat be able to evaporate.  That process is dependent on both the ambient temperature and the humidity.  The most common measure of the combination of the two is called the wet bulb temperature, which effectively measures how cool your skin can become through sweating alone.

Europe’s 2003 heatwave reached wet bulb temperatures of around 26 degrees Celsius.  The 2010 Russian heatwave reached wet bulb temperatures of about 28 degrees Celsius.  At a wet bulb temperature of 32 degrees Celsius, even people who are “used to the heat” stop being able to carry out normal outdoor activities.  A wet bulb temperature of 35 degrees Celsius is considered unsurvivable for more than a few hours.

To date, wet bulb temperatures like that are relatively rare.  There have been a few hours in the United Arab Emirates that have been that hot, a few more hours in Pakistan and Saudi Arabia.  So far, we have been lucky; we will not stay that way for long. 

MIT professor Elfatih Eltahir has modeled the maximum wet bulb temperatures across densely populated regions of Asia under different climate scenarios:

(Figure shows projected maximum wet bulb temperatures in India over the next 30 years)

Over the last thirty years (the leftmost panel), maximum wet bulb temperatures edged into the low 30s.  India is certainly hot and humid, but heat deaths are uncommon; it’s not fun to be outside some of the year, but it’s not actively dangerous.

The middle panel projects maximum wet bulb temperatures under a “moderate” emissions scenario, with about 2.25 degrees of warming.  This is a reasonably likely scenario, a reasonable approximation of what the world will look like in 30 years.

Even under this model, parts of India will be on the cusp of uninhabitable.  Every year would contain temperatures as high as the very hottest heatwaves today - and 45% of Indians still work outdoors, in agriculture.  55% of the population of this region will be expected to experience conditions that almost no humans have ever seen, under which outdoor work is completely impossible.  Indeed, if one tried to work outside in those conditions, your organs would essentially cook - multi-organ failure is likely.

Even on cooler days, life would look very different than it does today.  Remember that the US is already seeing increased crime, lower learning levels, and lower productivity - and 90% of American households have air conditioning.

In an environment where few people have air conditioning, the consequences would be much more severe.  Current research suggests productivity in India can drop as much as 4% per degree of warming - suggesting that under two degrees of warming, the whole economy would contract by 8%.  Under current heat projections, climate change alone could cause an economic depression.  There aren’t good projections of how many deaths would result from this level of heat, but it could easily be hundreds of thousands per year.3

And that’s not even the worst case scenario.  The rightmost panel shows wet bulb temperatures under RCP 8.5.  This model is becoming less likely as more climate policies are adopted, but it’s still possible.

According to Eltahir’s model, large swathes of south Asia would become basically uninhabitable. 75% of the population of South Asia will experience wet bulb temperatures that could be fatal to healthly adults at least once a year; 30% of South Asia will experience high temperatures above those of Europe’s 2003 heat wave most of the year.  The cities of Lucknow in Uttar Pradesh and Patna in Bihar (current populations 2.9 million and 2.2 million, respectively) would have annual high temperatures that exceed human survivability.

What Do We Do About This?

There are two billion people in South Asia.  Do we abandon all of the Deccan Plateau and hope we can relocate everyone somewhere cooler?  That seems difficult; even evacuating all of Lucknow and Patna seems unlikely.

Cue the humble air conditioner.

Heat waves do not have to be deadly; in the United States, the widespread use of air conditioning has decoupled the temperature-mortality relationship.  AC units already save more than 200,000 lives a year.

In countries where AC use is widespread, productivity can remain high even as the climate warms.  Indeed, Singapore’s founding prime minister, Lee Kuan Yew, credited air conditioning for Singapore’s high productivity.  For Yew, trying to run the government of a hot, humid country like Singapore, “air conditioning was a most important invention for us, perhaps one of the signal inventions of history.”  (Singapore, incidentally, has much lower rates of heat-related mortality than surrounding countries.)

Certainly, there will be challenges to making AC more common.  The French aren’t wrong; there could be climate consequences to scaling up AC usage.  Air conditioning causes about 3% of global greenhouse gas emissions already; it is anticipated that by 2050, air conditioning could emit as much carbon as all of road transport does now if grids are not decarbonized.

Even if countries use greener sources for energy, many electricity grids aren’t even robust enough for the anticipated added burden.  An AC unit doesn’t do much good in a blackout.

And, of course, ACs cost money; they can be unaffordable for some of the people who need them most.4  These are real challenges that will require substantial effort and investment to solve.

But solve them we must.  We must ignore the scolding editorials about how we just need to get used to the heat and give up our air conditioning; millions of lives depend on it.

The neural tube develops early in pregnancy and will (over the next eight months) develop into the central nervous system, brain and spinal cord.  At best, a problem with the neural tube means problems with these crucial systems;1 at worst, it can mean a baby that simply does not develop a brain or a spinal cord at all.2

Neural tube defects (NTDs) are one of the most common types of birth defect, and occur in 1 in 1,000 pregnancies.  In Europe, this means neural tube defects occur in about 5,000 pregnancies a year.  And in at least half of these pregnancies, they could have been avoided if countries required foods to be fortified with folate.

Neural tube defects are about twice as common if the pregnant person has low levels in folate.  Folate is also known as vitamin B9, and the body needs it to make new cells - an especially important task in a pregnant person.

The body can’t make folate on its own, so it must be obtained from food or supplements.  Leafy greens and some nuts are particularly full of folate, but the vast majority of women (91% in the UK) don’t get enough folate from their diet to prevent neural tube defects.  Therefore, the standard recommendation is that women who intend to become pregnant should take a prenatal vitamin containing 400 micrograms of folate.

However, simply telling women to take their prenatal vitamins isn’t really enough.  The neural tube closes - and problems can develop - about four weeks after conception.  This is before many women even know they’re pregnant!  Many women simply will not know that they need to be taking folate before it’s too late to prevent a neural tube defect.

Most countries around the world therefore require folate to be included in staple products like flour, ensuring that women have a sufficient amount of folate already in their system if they become pregnant.  This strategy has been extremely effective. In Chile, introducing fortification reduced NTD rates by 55%; in Argentina, by 50%; in Costa Rica by 58%; in Canada by 49%.  Every year, thousands of parents in these countries have healthy children because their governments have required food fortification.

And yet Europe has largely chosen to pass up this clear public health win.  Of the 87 countries that currently require food fortification, only two are in Europe - Kosovo and Moldova (with the UK to join them in 2026).

(Map from the Food Fortification Initiative)

European countries seem to have two major concerns about mandating food fortification (and increasing levels of folate in most of the population):

1. Excess folate might increase B-12-deficiency-associated cognitive decline in the elderly.

2. There was some observational evidence that high levels of folate were linked to increased cancer risk.

In 2000, the European Commission Scientific Committee on Food reviewed the evidence and concluded that “although there is no conclusive evidence in humans, the Committee concludes that the risk of progression of the neurological symptoms in vitamin B12 deficient patients… cannot be excluded and should be considered the most serious adverse effect”.  As a response, many countries in Europe declined to implement fortification out of an abundance of caution.

Nor was it only experts that were concerned about adding folate to food.  In 2003, a pilot program for fortification in France failed because the public was concerned about the adverse effects of folate.  Many Europeans believe all food additives are harmful, regardless of the type of additive.

It is true that it is important to make sure to “first, do no harm” when implementing public health policy.  However, with 25 years more of data on the safety of folate, these concerns do not seem to justify European countries’ continuing decision not to fortify.

Indeed, subsequent evidence has largely repudiated the idea that folate fortification is risky.  A later re-analysis showed that the study that linked cognitive decline and folate intake was flawed; the Food and Nutrition Board at the Institute of Medicine (IOM) of the National Academies now believes that “there is no level of folate which increases the risk of progression of the neurological symptoms in vitamin B12 deficient patients”.

Furthermore, randomized control trials show no link between folate levels and increased cancer risk.  Indeed, additional folate probably has more benefits than harms and may even reduce the risk of cancer.

All of this means that in 2024, the scientific consensus on folate fortification is clear.  Major medical journals (like the Lancet and the British Medical Journal) regularly run articles about the benefits of mandatory fortification.  The European Board and College of Obstetrics and Gynaecology has urged “European governments to consider the compelling evidence to make flour fortification with folic acid mandatory”.

And yet: most of Europe doesn’t appear to have updated their views of the risks adding folate to foods.

The consequences of this have been predictable: the rate of neural tube defects in Germany is roughly double that of Chile, and mothers in Sweden are 50% more likely to lose a child to a neural tube defect than those in Canada.

It is not that fortification is too hard to implement or too expensive.  Countries like Indonesia (GDP/capita $4800) and Iran (GDP/capita $4600) have managed it, and setting up mandatory fortification in Australia cost just $2.5 million AUD ($1.66 million USD).  Fortification seems well within the capabilities of the French or Dutch or German state.

And the benefits would far outweigh the costs.  Fortifying all the flour sold in Europe would cost perhaps $45,000,000 a year.3  The average cost of medical care for a single person with spina bifida is almost a million dollars - making the program cost effective if it prevented some 60 cases of spina bifida a year.  One systematic review estimated that on average, the benefits from fortification are some 17 times the costs.

As an example, the British National Health Service will generally pay for any treatments that cost £20,000-£30,000 per additional quality-adjusted life year (QALY) lived.  When Australia implemented fortification, it cost just £5871 per QALY gained.  If fortification was a medical treatment, it would be the best purchase the NHS could make.4

So why are European countries still so recalcitrant to add folate to staple foods?  I find it hard to understand.  Perhaps twenty years ago, the benefits were less clear and the risks seemed more significant.  But by now, some 80 countries have implemented folate fortification, and no adverse effects of these programs has yet been found.  And every year that Europe doesn’t implement fortification, more babies die, more children suffer, and more people terminate wanted pregnancies.5

Europe is a wealthy continent where people (largely) live long and healthy lives.  There simply aren’t that many easy public health wins left for European countries.  But food fortification is one - and it is time that Europe caught up with the rest of the world.

The majority of young people in sub-Saharan Africa want to leave their home countries. They have pretty understandable concerns about the places they live - and they want to go where there are good jobs, the government functions well, and where they can walk the streets without fear.

And the more educated they are, the more likely they are to be able to achieve their ambitions of leaving - and leave their home country for greener pastures. This is particularly true in the medical sector, where people have skills valued in almost every country.

In the seven years between 2011 and 2018, some 10% of doctors in Bhutan left the country for good. By 2017, 88% of Nigerian doctors were considering moving abroad. In the last decade, the number of doctors seeking to leave Turkey has increased a terrifying 70-fold (with no end in sight). What does the medical sector in these countries even look like in ten years?

Policymakers are certainly concerned about this; in 2010, the speaker of Parliament in Lebanon said brain drain was “the biggest problem we face”. In 2020, the WHO launched a program to stop rich countries from recruiting medical personnel from countries that desperately needed their doctors and nurses to stay at home. In 2023, Nigeria considered passing a law that would force all graduates from medical school to stay in the country for at least five years.

All of this policy concern is completely misplaced. Countries should encourage their skilled people to seek the best opportunities possible, even if it means leaving the country altogether.

Why? There are lots of ways that migrants contribute to their home country

Most obviously, many migrants send home money - perhaps 10-15% of what they earn. Since migrants can make 5-10x what they would at home, they can end up sending home as much as they would have earned if they hadn’t left - leaving both them and their families better off. Remittances pay for new homes, pay for more school for their kids, and let people get much needed medical care.1

In some cases, remittances power entire economies. About one in ten Hondurans and Kyrgyz people live abroad, but about a third of both economies is entirely remittances. It is hard to believe that Honduras or Kyrgyzstan would be better off if all those people returned home to far lower wages.

But policymakers don’t think remittances are good enough for migration to be worth it. If all the doctors in a country leave, the country will struggle no matter how much money those doctors send back; money is only good as far as you can purchase goods and services with it. And once all your doctors and nurses - and teachers and engineers and scientists - have gone, from whom will you purchase those services?

If the supply of doctors and nurses is fixed, this is a valid concern. In the real world, the supply of doctors isn’t fixed. When people have the option to earn qualifications in order to go abroad and earn more, they are much more likely to pursue those qualifications. When doctors can go abroad (and earn more), more people want to become doctors. Some of these additional doctors will end up leaving, but some will end up deciding not to.2

This is exactly what happened in the Philippines when US visa rules changed to make it easier to move there as a nurse. Many more Filipinos decided to train as nurses; new nursing colleges opened to accommodate the demand. Many of the newly trained nurses did end up moving, but not (even close to) the majority. Even after some left for the US, the Philippines ended up with considerably more nurses than they’d had before.

The same happened in the IT sector in India. Many people in India went to school and learned IT because they hoped to migrate to the US. But not all ended up getting visas to the US - and those that stayed behind helped start the Indian software boom. India did not end up worse off because people tried to migrate; instead, they ended up with more skilled people than ever before.

The logic makes sense. You’re probably more likely to enroll in a costly, time-consuming university course if you think you might move to another country and make more money than you’ve ever seen. But life happens; people get married, start families, and change their plans. Not everyone who thinks that they might want to go abroad will end up doing so.

Furthermore, many of those that do go abroad - almost 40% - eventually come home. In the interim, they’ve gained even more skills. Return migrants drive increases in productivity and are much more likely to start businesses and employ others upon return.

So policies to deter doctors from moving away from Nigeria are doing exactly the opposite thing that they’re intended to do. You might keep a few doctors from moving away, but far fewer Nigerians will want to become doctors. You might avoid brain drain - but you also avoid creating highly educated brains in the first place.

Instead, policymakers should accept that migration is a part of a globalized world. Developing countries do not lose out when highly educated people pursue opportunities around the world. Contra the Lebanese (and Nigerian and Turkish and Bhutanese…) government, brain drain isn’t a huge problem; indeed, it is… not actually a problem at all. International migration is a feature for developing countries; it’s not a bug.