4 ms·

> No, there is also technological development, wars and so on. Which have an effect on fertility and death rate. There is literally nothing that matters to pop

> No, there is also technological development, wars and so on. Which have an effect on fertility and death rate. There is literally nothing that matters to population dynamics other than fertility and death rate. We have extensive experience on that now: Technological and social development drives fertility to at or below replacement levels rapidly. This is the main factor. Importantly though, _this is not a prediction_. This reduction has already happened. So the bulk of the prediction is just playing out the consequences of developments we've already seen. Of course major events like climate change have the potential to invalidate this prediction. But that doesn't mean this prediction is useless. And this is would not be due to "sensitivity to initial inputs".

jacquesm 7y ago
> Which have an effect on fertility and death rate. Yes, but given that they are unknowns you can't just extrapolate from the presently available data and call it a day. > But that doesn't mean this prediction is useless. It's an open door that the world population will stabilize at some point, it is also an open door that the speed with which the world population is increasing itself is reducing. It has to, simply because more affluent people will have fewer children because they are not looking at their children as their source of income when they are themselves unable to generate any. Children as a pension scheme is a very common thing still, but that is fortunately changing. > And this is would not be due to "sensitivity to initial inputs". To a degree it is: any error in the predictions for the next couple of years will result in a much larger error in the future, simply because of the fact that population increase is a non-linear affair to begin with, and that any med-tech development that causes people to live longer will also cause a large increase in the number of people alive at any one moment. Compounded those two could have an enormous effect. For reference, the world, 80 years ago, so just before WWII had only 2.2 billion people.
- xorfish 7y ago
  > Children as a pension scheme is a very common thing still, but that is fortunately changing. It is still the case, just on a larger scale.
  - jacquesm 7y ago
    Good point.
- beat 7y ago
  It's more likely the rate of birth rate decrease will increase, rather than decrease. The countries hitting birth rate decreases over the last 50 years are seeing birth rate drops in a generation that took a century in Europe - and remember, not that long ago, Europe once had birth rates, illiteracy rates, and poverty as high as the poorest countries in the world today. Moreover, the major causes of birth rate decrease, like vaccination and refrigeration (which strongly impacts food supply), aren't going away. Look at a country with a high birth rate today, and you'll still find people walking for miles with buckets full of the day's water for their household. And anywhere that indoor plumbing and clean tap water is universal, the birth rate is down to replacement level. There are fundamental causes for birth rate decrease, and they're not going away. Frankly, I think you're clinging emotionally to the Malthusian model, not rationally.
challenger22 7y ago
I would argue that the primary mechanism is cultural changes effecting the fertility rate. Japan suffers a declining population not because of its technology, but because of its culture. Population growth rate peaked in 1968. Up until 1968, lots of evidence social scientists had to work with indicated that technological and social advancement increased the fertility rate (notwithstanding life expectancy changes and rich vs poor countries). Just because cultural changes over the past 51 years have been toward lower birth rates, does not mean that this will continue. You cannot predict the direction that culture will change. Any predictions I make about this are extremely speculative, but it is easily imaginable that 20 years from now the zeitgeist reacts against the corpus of current culture to be more family-oriented. Think about how much you hear people complain against "the machine." Whether it's on r/latestagecapitalism, or r/the_donald, everyone hates the piss out of broad society, and may find solace in tight-knit families.
- raducu 7y ago
  There's nothing "cultural" about birth rates. Raising children is hard, sex feels good, given the option to have sex and not have children, most people choose to have sex and not raise children. Atheist women choose not to have children, christian women choose not to, muslim women choose not to. Give people the option not to have children, remove the stigma and maybe they have 1-2 children, but no more. Given how many single people there are, how tight the fertility window is for women who have careers, how tight schedules are in big cities, how expensive it is to have children today, there's nothing we can reasonably do to increase birth rates.
  - challenger22 7y ago
    You state that there is nothing cultural about birth rates and then list several cultural factors influencing birth rates. And then you state that there is nothing we can reasonably do to increase birth rates, even though most of the factors you mentioned are not set in stone. I'm not even sure what you are trying to say.
    - raducu 7y ago

jacquesm 7y ago

> Which have an effect on fertility and death rate. Yes, but given that they are unknowns you can't just extrapolate from the presently available data and call it a day. > But that doesn't mean this prediction is useless. It's an open door that the world population will stabilize at some point, it is also an open door that the speed with which the world population is increasing itself is reducing. It has to, simply because more affluent people will have fewer children because they are not looking at their children as their source of income when they are themselves unable to generate any. Children as a pension scheme is a very common thing still, but that is fortunately changing. > And this is would not be due to "sensitivity to initial inputs". To a degree it is: any error in the predictions for the next couple of years will result in a much larger error in the future, simply because of the fact that population increase is a non-linear affair to begin with, and that any med-tech development that causes people to live longer will also cause a large increase in the number of people alive at any one moment. Compounded those two could have an enormous effect. For reference, the world, 80 years ago, so just before WWII had only 2.2 billion people.

xorfish 7y ago
> Children as a pension scheme is a very common thing still, but that is fortunately changing. It is still the case, just on a larger scale.
- jacquesm 7y ago
  Good point.
beat 7y ago
It's more likely the rate of birth rate decrease will increase, rather than decrease. The countries hitting birth rate decreases over the last 50 years are seeing birth rate drops in a generation that took a century in Europe - and remember, not that long ago, Europe once had birth rates, illiteracy rates, and poverty as high as the poorest countries in the world today. Moreover, the major causes of birth rate decrease, like vaccination and refrigeration (which strongly impacts food supply), aren't going away. Look at a country with a high birth rate today, and you'll still find people walking for miles with buckets full of the day's water for their household. And anywhere that indoor plumbing and clean tap water is universal, the birth rate is down to replacement level. There are fundamental causes for birth rate decrease, and they're not going away. Frankly, I think you're clinging emotionally to the Malthusian model, not rationally.

challenger22 7y ago

I would argue that the primary mechanism is cultural changes effecting the fertility rate. Japan suffers a declining population not because of its technology, but because of its culture. Population growth rate peaked in 1968. Up until 1968, lots of evidence social scientists had to work with indicated that technological and social advancement increased the fertility rate (notwithstanding life expectancy changes and rich vs poor countries). Just because cultural changes over the past 51 years have been toward lower birth rates, does not mean that this will continue. You cannot predict the direction that culture will change. Any predictions I make about this are extremely speculative, but it is easily imaginable that 20 years from now the zeitgeist reacts against the corpus of current culture to be more family-oriented. Think about how much you hear people complain against "the machine." Whether it's on r/latestagecapitalism, or r/the_donald, everyone hates the piss out of broad society, and may find solace in tight-knit families.

raducu 7y ago
There's nothing "cultural" about birth rates. Raising children is hard, sex feels good, given the option to have sex and not have children, most people choose to have sex and not raise children. Atheist women choose not to have children, christian women choose not to, muslim women choose not to. Give people the option not to have children, remove the stigma and maybe they have 1-2 children, but no more. Given how many single people there are, how tight the fertility window is for women who have careers, how tight schedules are in big cities, how expensive it is to have children today, there's nothing we can reasonably do to increase birth rates.
- challenger22 7y ago
  You state that there is nothing cultural about birth rates and then list several cultural factors influencing birth rates. And then you state that there is nothing we can reasonably do to increase birth rates, even though most of the factors you mentioned are not set in stone. I'm not even sure what you are trying to say.
  - raducu 7y ago