“World population growth could slow from 2065 onwards”

The Aus­tri­an demo­graph­er Wolfgang Lutz pre­dicts a decline in the world’s pop­u­la­tion from 2065 onwards, where­as people are more likely to speak of a “demo­graph­ic per­il” by 2050. What can we say about the long-term evol­u­tion of the population?

If we look at the evol­u­tion of the annu­al pop­u­la­tion growth rate, it peaks at 2.1% in 1975 (i.e., a doub­ling every 33 years), then decreases to 1% today and could be can­celled out by 2065, when the pop­u­la­tion would begin to decline. 

Nev­er­the­less, when mak­ing pre­dic­tions bey­ond 2050, past errors have taught us to handle fore­casts with cau­tion. For example, in 1994, the United Nations Pop­u­la­tion Divi­sion pro­jec­ted 163 mil­lion Ira­ni­ans by 2050 and is now pro­ject­ing 103 mil­lion after drop­ping to 94 mil­lion in 2014. In the mean­time, fer­til­ity has dropped from 6.5 chil­dren per woman to 1.7, then back up to 1.9. The same is true for France, which in 1994 was pro­jec­ted to have 60 mil­lion inhab­it­ants in 2050 and now pro­jects 74 mil­lion. The rise in the birth rate at the end of the 1990s was poorly anti­cip­ated, as was net migration.

The medi­an fore­cast of the United Nations is for con­tinu­ous growth until 2100 and a pop­u­la­tion of 11.2 bil­lion people by that date. Should we doubt this fore­cast in light of the work of Wolfgang Lutz?

There are sev­er­al reas­ons to doubt it. The United Nations pre­dicts a slow decline in fer­til­ity in inter­trop­ic­al Africa (between the Saha­ra and the Zam­bezi), even though this area accounts for a quarter of the world’s pop­u­la­tion growth and will account for three quar­ters by 2050. For example, the United Nations pre­dicts that Niger, the world’s fer­til­ity cham­pi­on, will drop from 7.3 chil­dren per woman to 4 in 2050 and 2.5 in 2100. How­ever, much faster declines have occurred in the recent past. Between 1985 and 2005, fer­til­ity was halved in South Africa, from 5 to 2.6 chil­dren per woman, and it fell from 6.5 to 1.9 in Iran over the same period.

Pro­jec­tion of the world pop­u­la­tion until 2100 © ONU

Second, the UN pre­dicts baby booms in sev­er­al coun­tries with very low fer­til­ity, such as South Korea (0.98) and Singa­pore (1.14). When fer­til­ity is below 1.3 chil­dren per woman, the United Nations sys­tem­at­ic­ally fore­casts an increase to 1.5 by 2050, then to 1.7 or 1.8 by 2100. Indeed, fer­til­ity rates are rising again after sharp declines. We can cite the case of the former East­ern bloc coun­tries, which exper­i­enced a sharp drop in fer­til­ity linked to the decline in the age of first child (from 23 to 28). How­ever, once the trans­ition was com­pleted, there was a return to nor­mal and a slight increase, albeit mod­er­ate. In Poland, the num­ber of chil­dren per woman rose from 1.24 in 2004 to 1.41 in 2011 and in Hun­gary from 1.25 to 1.39 from 2011 to 2016. Then fer­til­ity fell back down. These mech­an­ic­al effects are insuf­fi­cient to jus­ti­fy the UN projections.

Is fer­til­ity misjudged?

On the whole, the decline in fer­til­ity is fairly poorly anti­cip­ated. Two-thirds of the world’s pop­u­la­tion live in a coun­try where fer­til­ity is below two chil­dren per woman. In Lat­in Amer­ica, the coun­try – or region – with the highest fer­til­ity is French Guyana! Brazil has gone from 6.5 chil­dren per woman to 1.7 in 40 years. 

Finally, the two most pop­u­lous coun­tries, China and India, are exper­i­en­cing a rap­id decline in fer­til­ity. In India, it is already 2.3 chil­dren per woman and in 23 out of 36 states below 2.1. In China, the aban­don­ment of the one-child policy in 2017 gen­er­ated a slight increase that has since fully sub­sided. But again, the demo­graph­ic trans­ition has a lag effect. China, to use this example, will only exper­i­ence a decline in pop­u­la­tion from 2032 onwards. 

Do you see oth­er reas­ons for over­es­tim­at­ing pop­u­la­tion growth?

Yes, the decline in mor­tal­ity seems to be over­es­tim­ated. This con­trib­utes to the demo­graph­ic boom because people are liv­ing longer. How­ever, over the past five years, the aver­age age of death has increased much more slowly in developed coun­tries. Pos­sible causes include obesity, envir­on­ment­al degrad­a­tion, and inequal­ity. How­ever, the UN expects a gain of five years of life by 2030 in these coun­tries. This seems very optimistic. 

What will the world pop­u­la­tion be in 2100?

It will not reach 11 bil­lion, but rather 10 bil­lion. We can say that the pop­u­la­tion explo­sion is almost over. The explo­sion of the 1990s and 2000s is behind us and the decline will come soon­er than we think.

What could be the con­sequences of this demo­graph­ic decline?

I see two major soci­et­al changes. The neces­sary delay in retire­ment in coun­tries that have a pen­sion sys­tem (to main­tain it), and the entry of women into the work­force in coun­tries where their par­ti­cip­a­tion rate is low. In both cases, this requires a change in men­tal­ity. We see this in France with retire­ment. The philo­soph­er Mar­cel Gauchet talks about the “social­ist moment” of life: free time, money and no more boss! Many people do not want to give it up. 

As for health costs, they are really con­cen­trated in the last months of people’s lives. The decline in mor­tal­ity post­pones health costs more than it increases them, all oth­er things being equal.

Interview by Clément Boulle