Migrate to survive
There is an immigration problem in many developed countries. Besides people who flee wars and persecution, there is an (often larger) number of economic refugees coming to Europe, Australia, and the US in search of better job opportunities. A key driver of this is environmental degradation and climate change, which is only going to get worse in the future. Ironically, in the past, it is exactly this kind of economic migration from Europe to the US that helped European countries ease economic pressures.
Look at the chart below which is not that easy to read, so I will explain it in some detail. The horizontal axis looks at the people living in different countries in the year 2000. Then, for each country, the researchers calculated what share of the current population is descendent from people who lived in the same country 500 years ago in 1500. If a dot is more to the right, it means there are fewer immigrants living in the country today (where immigrants are people who didn’t have an ancestor in the country 500 years ago). Note that France is further to the left than the UK, which is further to the left than Ireland. This simply shows that there was more immigration to France than the UK over the last 500 years and more immigration to the UK than to Ireland.
The vertical axis looks at the population in each country in the year 1500 and calculates what percentage of the descendants of these people still live in the same country. Countries that are lower on the chart have seen a larger share of their population emigrate to other countries. In other words, there has been fewer emigration from France to other countries than from the UK. And of course, most people with Irish ancestry now don’t live in Ireland, but all over the world.
Population flows over the last 500 years
Source: Blanc and Wacziarg (2025)
Guillaume Blanc from the University of Manchester and Romain Wacziarg from UCLA examined what caused these differences between countries. They find that the main driver were fertility rates. Countries with higher birth rates had more emigration. But it wasn’t just overpopulation. Anyone even superficially familiar with the history of Ireland knows that emigration happened in waves and were commonly triggered by environmental factors like the potato famine.
Emigrants per capita to the US as a function of fertility rates in the 19th century
Source: Blanc and Wacziarg (2025). Note: Blue dots indicate the example of France over time.
Today, we can still see these patterns in action. Countries with higher fertility rates have higher emigration rates. Countries with very low fertility rates also have somewhat higher emigration rates. The latter is a reflection of the increased mobility of highly trained, cosmopolitan people living in the most developed countries in the world (i.e. people like yours truly).
Determinants of emigration today, in a panel of countries
Source: Blanc and Wacziarg (2025)
The more things change, the more things stay the same then. But what I find particularly interesting about the study of Blanc and Wacziarg is that they find that higher emigration from (over?)populated countries facing a natural crisis like a famine helped the rest of the people who stayed. Countries with higher emigration rates subsequently had higher growth and developed faster. If it weren’t for the people moving to the US or the colonies, the UK, Ireland, etc. would be much poorer today.
And ironically, if there were more people available as cheap labour in the British Empire in the 18th and 19th century, the industrial revolution might never have been adopted as fast as it was because business owners would have just relied on cheap labour rather than invest in machinery.
But today, we are at the receiving end of the migratory streams and some people are worried that we can’t deal with this influx. So, what to do about it? How can we reduce the number of immigrants coming to Europe or the US?
The charts above provide a straightforward answer. In the past, just like today, an effective tool against excessive immigration is to lower the birth rates in the countries where the immigrants come from. And you know what the best way is to do that? It is by investing in foreign aid and by investing in education in developing countries. Because there is a ton of evidence that people have fewer children if they have a better education. Better education gives people better economic prospects and reduces their need to rely on their children to support them in old age.
Meanwhile in the US and the UK, we are cutting our international aid funding to effectively zero…
"The more things change, the more things stay the same then. But what I find particularly interesting about the study of Blanc and Wacziarg is that they find that higher emigration from (over?)populated countries facing a natural crisis like a famine helped the rest of the people who stayed. Countries with higher emigration rates subsequently had higher growth and developed faster. If it weren’t for the people moving to the US or the colonies, the UK, Ireland, etc. would be much poorer today."
It isn't clear to me from the text, but over what timeframe is that final chart? If it captures German, UK, and Irish emigration to North America in the seventeenth-twentieth centuries, one could indeed conclude that emigration helps the home country by reducing labor competition and driving technological innovation to fill the gap. But there *were* more than ample sources of cheap labor for Britain in the eighteenth and nineteenth century, namely millions of colonized people and slavery (early on for Britain directly with sugar and rum, but continuing by proxy through its dependence on cotton from the southern US). And if the timeframe is long enough, it doubtless reflects remittances, always a feature of emigration but one that accelerated once people could wire money home.
I completely agree with you that the return on investment on foreign aid is very high, and that we cut it at our peril.
Interesting opinion. Although I like to advise you to read the landmark book How migration really works, written by professor Hein de Haas, a Dutch scholar on migration. He places migration also in a broad historical perspective. Funfact: the main fundings are not foreign direct investment and official development assistance, but the remittances of the migrant workers. Estimates, made by the Worldbank, are about $ 905 billion (2024).