Empty Planet: The shock of global population decline (2019, Bricker & Ibbitson)

[markbike528CBX]

Both population growth and population decline can cause serious problems.  I don't think your generation even considered the latter a possibility, but now it's looking much more likely that population in the 21st century will see a steep decline instead of any kind of large increase like in the 20th century.  I think that some kind of population stability would be the ideal. 

Globally? I thought the most conservative projections were flat to slightly declining between 2050 and 2100. But I could be out of date, let me know if I am.

If you look at projections for the Japan, China, Europe, yes, it does look like we're in for some pretty steep declines after 2050. In the US the x-factor is whether we continuing to invite in immigrants from the rest of the world. If so, we'll grow more slowly or stabilize. If not, we'll start to look more like Japan/Europe in terms of shrinking population.

The current UN projection is population to hit 9.5B in 2050 and 11B in 2100. The theory of this book that the thread is titled after is that the population will instead peak at 9.5B around 2040-2060 and then fall back down to 7.5B by 2100.

This depends on world fertility rate hitting replacements levels by 2025. We're currently at 2.4 (2019) and dropping. We'll have a better idea about our projection in a few years to see if birthrates continue to remain at 2.4 or drop to replacement levels.

A big factor is the unevenness of the population change.

From the US Census estimates of population in 2000 and 2050, the following extremes are shown.

        Population change   % change population      Population Rank change
          India                       Madagascar                 Madagascar
MAX      598,296,281              322%                          32
min      -27,767,933             -45%                           -40
          Russia                     Trinidad                        Bulgaria

Russia's population percentage change might be -19%, and it loses 8 spots on the population rank list.   If Putin does nothing his age 97 future empire shrinks.

[FIPurpose]

Both population growth and population decline can cause serious problems.  I don't think your generation even considered the latter a possibility, but now it's looking much more likely that population in the 21st century will see a steep decline instead of any kind of large increase like in the 20th century.  I think that some kind of population stability would be the ideal. 

Globally? I thought the most conservative projections were flat to slightly declining between 2050 and 2100. But I could be out of date, let me know if I am.

If you look at projections for the Japan, China, Europe, yes, it does look like we're in for some pretty steep declines after 2050. In the US the x-factor is whether we continuing to invite in immigrants from the rest of the world. If so, we'll grow more slowly or stabilize. If not, we'll start to look more like Japan/Europe in terms of shrinking population.

The current UN projection is population to hit 9.5B in 2050 and 11B in 2100. The theory of this book that the thread is titled after is that the population will instead peak at 9.5B around 2040-2060 and then fall back down to 7.5B by 2100.

This depends on world fertility rate hitting replacements levels by 2025. We're currently at 2.4 (2019) and dropping. We'll have a better idea about our projection in a few years to see if birthrates continue to remain at 2.4 or drop to replacement levels.

A big factor is the unevenness of the population change.

From the US Census estimates of population in 2000 and 2050, the following extremes are shown.

        Population change   % change population      Population Rank change
          India                       Madagascar                 Madagascar
MAX      598,296,281              322%                          32
min      -27,767,933             -45%                           -40
          Russia                     Trinidad                        Bulgaria

Russia's population percentage change might be -19%, and it loses 8 spots on the population rank list.   If Putin does nothing his age 97 future empire shrinks.

Individual country changes say less about global population. Japan is dropping in population mostly from declining birth rates, but Russia is losing more people from emigration. It's 2 different problems. Overall global fertility is dropping, but I don't know that it's falling fast enough to meet the figures for the population decline from the 2019 paper.

Replacement rate is 2.1, but 2021's fertility rate came in at 2.44, down from 2020's 2.45. 4 more years to hit 2.1? It doesn't look like it's going to happen unless something major changes in places like Nigeria et al.

[maizefolk]

For a long time Russia's population was also dropping due to reductions in life expectancy. They've finally turned that around a bit but it's still shockingly low (two decades ago, a boy born in Russia could expect to live to 59, now he'd expect to live to 65) and driven in significant part from the same sorts of "deaths of despair" -- suicides, overdoses, liver and lung disease -- we're seeing more and more of here in the USA.

[AlanStache]

A gradual population decline has been listed as one of the "great filters" for why there are no little green men running all around.  Ie advanced civilizations birth rates fall below replacement levels until they just sort of stop existing.  We are clearly a long way away from this, and it is not a reason for exponential growth but maintaining (establishing, identifying?) an appropriate number of people will likely be something humanity has to think about for a long time if not for the reset of our existence.  In the The Spiral Wars (Joel Shepherd), set in the distant future where humanity spans the universe there are very active & strong incentives for reproduction given to women.  In the here and now I expect it would be very hard to find anyone in the hard sciences who would go along with the "science will solve our problems and figure out how to provide for exponential growth of global population" sentiment. 

Part of Putin's motivation I understand is also that he wants a natural land boarder on the west, this might be a minor point compared to others but had not seen it listed. 

[MarciaB]

The website www.populationpyramid.net has some great historical data and also future projections (which update as new info comes in).

[frugalecon]

For a long time Russia's population was also dropping due to reductions in life expectancy. They've finally turned that around a bit but it's still shockingly low (two decades ago, a boy born in Russia could expect to live to 59, now he'd expect to live to 65) and driven in significant part from the same sorts of "deaths of despair" -- suicides, overdoses, liver and lung disease -- we're seeing more and more of here in the USA.

According to the World Bank (https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?locations=RU), Russia’s birth rate is about 1.5 kids/woman, which is way below replacement rate. That will tend to cause its population to drop regardless of what happens to life expectancy (at least in the long run). It is interesting that Homo sapiens may return to being predominately an African species, since Africa is the only continent that is still projected to grow meaningfully. (Though I wonder if those projections will be realized…)

[MarciaB]

For a long time Russia's population was also dropping due to reductions in life expectancy. They've finally turned that around a bit but it's still shockingly low (two decades ago, a boy born in Russia could expect to live to 59, now he'd expect to live to 65) and driven in significant part from the same sorts of "deaths of despair" -- suicides, overdoses, liver and lung disease -- we're seeing more and more of here in the USA.

According to the World Bank (https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?locations=RU), Russia’s birth rate is about 1.5 kids/woman, which is way below replacement rate. That will tend to cause its population to drop regardless of what happens to life expectancy (at least in the long run). It is interesting that Homo sapiens may return to being predominately an African species, since Africa is the only continent that is still projected to grow meaningfully. (Though I wonder if those projections will be realized…)

Can you elaborate on this? I'm always interested in people's thoughts and predictions on these topics.

[frugalecon]

For a long time Russia's population was also dropping due to reductions in life expectancy. They've finally turned that around a bit but it's still shockingly low (two decades ago, a boy born in Russia could expect to live to 59, now he'd expect to live to 65) and driven in significant part from the same sorts of "deaths of despair" -- suicides, overdoses, liver and lung disease -- we're seeing more and more of here in the USA.

According to the World Bank (https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?locations=RU), Russia’s birth rate is about 1.5 kids/woman, which is way below replacement rate. That will tend to cause its population to drop regardless of what happens to life expectancy (at least in the long run). It is interesting that Homo sapiens may return to being predominately an African species, since Africa is the only continent that is still projected to grow meaningfully. (Though I wonder if those projections will be realized…)

Can you elaborate on this? I'm always interested in people's thoughts and predictions on these topics.

Many predictions were made about population growth in the 70s, and many of those have not come to pass. I think the transition to lower fertility in a lot of countries has been surprising. I guess sub-Saharan Africa may have 3.5 billion people in 2100 (roughly half the population of humans today, this is in the range of current predictions), but I wonder. If African urbanizes significantly, that would likely reduce population growth. So might environmental catastrophe. So might mass migration to an empty Europe. It’s hard to say. I don’t have a well-thought-out hypothesis, just skepticism about predictions far in the future.