5 ms·

Frome wikipedia: "Global human population growth amounts to around 75 million annually, or 1.1% per year." 1.1% is exponential growth when the base is growing,

Frome wikipedia: "Global human population growth amounts to around 75 million annually, or 1.1% per year." 1.1% is exponential growth when the base is growing, just like 1.1% compound interest displays exponential growth. It is still growing exponentially, although the rate is declining.

atemerev 9y ago
If the rate is declining, the growth is no longer exponential :)
- ljw1001 9y ago
  picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population" whatever it is, is still growing exponentially at the less steep curve.
  - maxerickson 9y ago
    The idea is that an exponential curve is no longer the correct model for forecasting growth past 2070. Arguing about how to express that is sort of pointless.
    - candiodari 9y ago
      Population growth in non-human species is quite well documented and is in fact not exponential, although the early stages look exponential. It is in fact a logistic sigmoid function. It is amazing, in that it is not what you'd expect : clearly the vast majority of species have the ability to correctly estimate the carrying capacity of a habitat and only overshoot by a little bit. So the Malthusian argument is incorrect, probably, if humans are like other animals (and since population growth curves in many localities do indeed look like S-curves I would say that this ought to be the default claim). Human population size will by itself stop just shy of the carrying capacity of the planet. Which is exactly what you'd want to happen. In all likelihood, this will happen without active measures from governments (which won't work anyway due to the global nature of the required policies), with or without popularizing contraceptives, with or without female labor participation, ... (not saying those aren't desirable, just that they aren't necessary) The alternative requires an assumption that humans are hugely different from the species that we evolved from, and since this certainly isn't true in the biological sense, why would our population growth be so very different ? Humans are not the first large animal to "conquer the planet", and reach population numbers in the billions, with some fish well on the way to trillions even today, and we aren't the biggest species in terms of total biomass by a very long way (amongst non-plants that honour likely goes to ants, but even pathetic species of bacteria dwarf their numbers). Will we be the last one ? Perhaps, but it seems unlikely. https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_modeling_population_growth https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_...
      - nostrademons 9y ago
        It's not that species have the ability to correctly estimate the carrying capacity of the environment. It's that when the population of a species exceeds the carrying capacity of the environment, individuals will die and/or fail to reproduce, dropping the population of the next generation. It's very likely that humans exhibit the same behavior, but on a micro-scale, this isn't very comforting. If a politician says "Well, the earth will be fine, but 10% of you are gonna die and another 30% won't be able to have children that survive to adulthood", there would be rioting on the streets ... which has a non-negligible chance of bringing about those numbers. Nature will be just fine, but remember that the mechanisms by which nature self-adapts are the four horsemen of the apocalypse: pestilence, war, famine, and death.
      - dualogy 9y ago
        > So the Malthusian argument is incorrect, probably, if humans are like other animals > The alternative requires an assumption that humans are hugely different from the species that we evolved from Well we are, for proof look at the fact that we're even discussing it here when all the other species never did. Look, that all sounds very peachy if it weren't for the fact that our species alone has grown the brains and the self-justifications for consciously attempting to continously outwit "nature" (and be able to replicate way beyond what our ancestral habitats could carry) at every turn with agriculture and all the sciences =) granted, there's no point in or way of "going back" for all manner of reasons, but we needn't lose sight of certain basic facts here..
      - ljw1001 9y ago
        I refer you to the 12,000-year human population growth chart on Our World In Data, in a post by Max Roser. https://ourworldindata.org/world-population-growth/ https://ourworldindata.org/world-population-growth/ Growth is clearly exponential. Your theories don't fit the data.
        candiodari 9y ago
        I'm looking at that graph. I see a spike in the growth rate, after the spike it goes to zero. I'm not an expert (I have a masters in statistics actually) but that doesn't look very exponential to me. Can you explain what I'm missing ?
- spiraldancing 9y ago
  2% is exponential growth; 1% is still exponential growth. Decrease from 2% to 1% is a decrease in the rate of growth, which still remains exponential.
  - atemerev 9y ago
    (Sigh). Look at the linear function. It experiences "decrease in the rate of growth" along the line. If the exponent is not constant, we do not have "exponential growth" anymore — by definition.
deleted 9y ago
[deleted]
ljw1001 9y ago
picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population" whatever it is, is still growing exponentially at the less steep curve.
- ljw1001 9y ago
  LOL. somebody downvoted this, but you know. Math.
  - Rexxar 9y ago
    People like to use percentage for everything. That doesn't mean that everything is exponential.
    - ljw1001 9y ago
      No, but we are talking about a formula of the type where a growth rate G is a factor of a base population P, and P in Period n+1 = P(n) + G*P(n) In this case G is the difference between the birth rate and the death rate for time period t. As long as a G is positive, you get exponential growth. Every time. This is how compound interest works. The fact that your balance next year is based on your starting balance + the balance multiplied by a positive growth rate ALWAYS leads to exponential growth in the balance. Here's a video that explains it. https://www.youtube.com/watch?v=NB4KVSjgi24 https://www.youtube.com/watch?v=NB4KVSjgi24
      - atemerev 9y ago
        > In this case G is the difference between the birth rate and the death rate for time period t OK then. Let the birth rate be 1 person per second and death rate 0 (nobody dies). Do you get exponential growth? No. This is still linear growth. Your another mistake is that ax^b is exponential growth, and ax^c is also exponential growth (if b and c are constants), but these are different processes. If you get a single process with changing exponent, this is no longer exponential growth, it can be arbitrarily defined.

atemerev 9y ago

If the rate is declining, the growth is no longer exponential :)

ljw1001 9y ago
picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population" whatever it is, is still growing exponentially at the less steep curve.
- maxerickson 9y ago
  The idea is that an exponential curve is no longer the correct model for forecasting growth past 2070. Arguing about how to express that is sort of pointless.
  - candiodari 9y ago
    Population growth in non-human species is quite well documented and is in fact not exponential, although the early stages look exponential. It is in fact a logistic sigmoid function. It is amazing, in that it is not what you'd expect : clearly the vast majority of species have the ability to correctly estimate the carrying capacity of a habitat and only overshoot by a little bit. So the Malthusian argument is incorrect, probably, if humans are like other animals (and since population growth curves in many localities do indeed look like S-curves I would say that this ought to be the default claim). Human population size will by itself stop just shy of the carrying capacity of the planet. Which is exactly what you'd want to happen. In all likelihood, this will happen without active measures from governments (which won't work anyway due to the global nature of the required policies), with or without popularizing contraceptives, with or without female labor participation, ... (not saying those aren't desirable, just that they aren't necessary) The alternative requires an assumption that humans are hugely different from the species that we evolved from, and since this certainly isn't true in the biological sense, why would our population growth be so very different ? Humans are not the first large animal to "conquer the planet", and reach population numbers in the billions, with some fish well on the way to trillions even today, and we aren't the biggest species in terms of total biomass by a very long way (amongst non-plants that honour likely goes to ants, but even pathetic species of bacteria dwarf their numbers). Will we be the last one ? Perhaps, but it seems unlikely. https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_modeling_population_growth https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_...
    - nostrademons 9y ago
      It's not that species have the ability to correctly estimate the carrying capacity of the environment. It's that when the population of a species exceeds the carrying capacity of the environment, individuals will die and/or fail to reproduce, dropping the population of the next generation. It's very likely that humans exhibit the same behavior, but on a micro-scale, this isn't very comforting. If a politician says "Well, the earth will be fine, but 10% of you are gonna die and another 30% won't be able to have children that survive to adulthood", there would be rioting on the streets ... which has a non-negligible chance of bringing about those numbers. Nature will be just fine, but remember that the mechanisms by which nature self-adapts are the four horsemen of the apocalypse: pestilence, war, famine, and death.
    - dualogy 9y ago
      > So the Malthusian argument is incorrect, probably, if humans are like other animals > The alternative requires an assumption that humans are hugely different from the species that we evolved from Well we are, for proof look at the fact that we're even discussing it here when all the other species never did. Look, that all sounds very peachy if it weren't for the fact that our species alone has grown the brains and the self-justifications for consciously attempting to continously outwit "nature" (and be able to replicate way beyond what our ancestral habitats could carry) at every turn with agriculture and all the sciences =) granted, there's no point in or way of "going back" for all manner of reasons, but we needn't lose sight of certain basic facts here..
    - ljw1001 9y ago
      I refer you to the 12,000-year human population growth chart on Our World In Data, in a post by Max Roser. https://ourworldindata.org/world-population-growth/ https://ourworldindata.org/world-population-growth/ Growth is clearly exponential. Your theories don't fit the data.
      - candiodari 9y ago
        I'm looking at that graph. I see a spike in the growth rate, after the spike it goes to zero. I'm not an expert (I have a masters in statistics actually) but that doesn't look very exponential to me. Can you explain what I'm missing ?
spiraldancing 9y ago
2% is exponential growth; 1% is still exponential growth. Decrease from 2% to 1% is a decrease in the rate of growth, which still remains exponential.
- atemerev 9y ago
  (Sigh). Look at the linear function. It experiences "decrease in the rate of growth" along the line. If the exponent is not constant, we do not have "exponential growth" anymore — by definition.

deleted 9y ago

[deleted]

ljw1001 9y ago

picture two exponential growth curves, one steeper than the other, over time the a trend moves from the steeper curve to the less steep curve. The "population" whatever it is, is still growing exponentially at the less steep curve.

ljw1001 9y ago
LOL. somebody downvoted this, but you know. Math.
- Rexxar 9y ago
  People like to use percentage for everything. That doesn't mean that everything is exponential.
  - ljw1001 9y ago
    No, but we are talking about a formula of the type where a growth rate G is a factor of a base population P, and P in Period n+1 = P(n) + G*P(n) In this case G is the difference between the birth rate and the death rate for time period t. As long as a G is positive, you get exponential growth. Every time. This is how compound interest works. The fact that your balance next year is based on your starting balance + the balance multiplied by a positive growth rate ALWAYS leads to exponential growth in the balance. Here's a video that explains it. https://www.youtube.com/watch?v=NB4KVSjgi24 https://www.youtube.com/watch?v=NB4KVSjgi24
    - atemerev 9y ago
      > In this case G is the difference between the birth rate and the death rate for time period t OK then. Let the birth rate be 1 person per second and death rate 0 (nobody dies). Do you get exponential growth? No. This is still linear growth. Your another mistake is that ax^b is exponential growth, and ax^c is also exponential growth (if b and c are constants), but these are different processes. If you get a single process with changing exponent, this is no longer exponential growth, it can be arbitrarily defined.