Population growth is S-shaped, not exponential

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  • Sat, Apr 10, 2010 - 10:27am

    #11
    Peak Prosperity Admin

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    Re: Population growth is S-shaped, not exponential

Sorry for bringing an old thread to life.

In many areas we have to guess pretty big what even the next 10 years will be, even if we have some facts. Oil production is one good example. Experts disagree from increased production to heavilly declining production.

However in the population growth we basicly know most of the facts for at least the next 25 years, and that really makes a difference.
Lets assume every female has an average lifespan of 70 years and very few of them have children after age of 45.
So, we know pretty well how long people will live, and we know pretty well the birthrate in every country in the world.
That means it is no problem to predict the next 25 years with a predicted error of only a few percent.

Here is a link to a page with a graph about possible Population growth.

We know that we are aiming for a scenario slightly above the TFR 2.1 curve with slowly dropping fertillity rates.
So, when just looking at fertillity rates and the most likely development of that front we are going to slowly reaching the max out point of about 10 billions in world population.

What is scarier is that normally we estimate that the average lifespan will be fairly constant.
There are many factors saying that this is not likely to be the case.
Currently the world average lifespan is slightly less than 70 years. In the best developed countries we allready start to pass 85 years. With advances in medical science and increased wealth it is likely that this limit will be pushed a lot further, at least to over 100 years.
For the sake of argument lets say by 2100 we have increased average lifespan to double what we have today (so we are closing in on 140 years). Then we will end up with a world population of about 20 billion.

Still I claim we are not heading for exponential population growth, but will approach a steady level.
If you believe in this the next question is: Can we sustain 10-15 billion people on this planet by 2050?

 

  • Sun, Dec 16, 2012 - 08:11pm

    #12
    Dustoffer

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    boom and crash curve

The human population is following the classic half bell shaped boom and crash curve.  By mid century a combination of various depletion and pollution effects will lower food and water supply to only enough for  perhaps 3 billion by mid-century.   A crash in population must occur then or before, starting with increasing death rates along with the already falling birth rates.   It is ignorant to think that this will not happen, when biology and ecology tell us it will in population science, which I have studied since 1967.

One doesn’t need to just look at exponential math, or  economics.  Rates of soil depletion from over-use and other causes, fisheries depletion, aquifer depletion, and oil depletion, along with pollution effects of mainly CAGW, dictate this lower food and water supply before or at mid century.  To stop the crash would take a near moratorium on having kids for 20 years followed by one child families until a new sustainable level is reached.   To stop extinction of our own species and nearly 90% of others, circa 3000AD, would require reduction in emissions of 90% by 2020 or the methane turnover scenario will lead to AETM and ELE completion, with several hundred thousand years to resequester the CO2 and another several million to regain biodiversity in the biosphere.

It is unfortunate that this is the way it really is, and not  the S curve hoped, but not supported.

  • Tue, Feb 19, 2013 - 03:35pm

    #14
    TheWind777

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    I Also…

Took the exact same bacterial curve and matched it to America's Stock Market just to see what would happen; again, it seems to be an exponential curve. What it shows is… the current trend is just a trend… it will keep going up for a time, then flatten-off, and by 2070 it will-have completely plummetted. So, it's not going to go balistically-low for another 60 years. So be prepared for a steep upwards trend in the stock market. Then that stubborn flat period between 2020 and 2050 when it flattens-out. Heh, heh. But it will go back up again, don't worry. Yeah, right. 

 

OK, that's using the most depressing figures. Using the most hopeful figures shows that we go upward with the stock market until 2040, where it starts to flatten-out. It then will stay flat until 2070 and then plummet down until in 2115 it will be as flat as it was back in 1950.

That in no way means we will easily be able to grow back to an exponential again, immediately, by then. Just as with bacteria, they don't immediately bounce-back again in that petri dish.

So, the secret is: get as good a true bacterial growth curve as you can. Don't use a curve which is just a theoretical curve. It must be an actual curve of measured bacterial growth and that should give true figures.

  • Tue, Feb 19, 2013 - 03:41pm

    #15
    TheWind777

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    What is one of the factors that make us the same as bacteria?

Capitalism.

Capitalism is what forces everybody to not listen. It, itself, is an exponential curve and therefore has mechanisms in place which force people to keep growing exponentially. If they stop growing exponentially, or even try and slow-down the curve (Republicans and rich people) then those people say lies which raise the curve again. The workers also go right along with it because the instant someone loses their job, they need to have a job again or it means death to that organism and that organism's family. If 'morals' are what counter the curve, morals go out the window the instant that someone loses their job. They'll instantly do anything at all in order to keep their family unit intact. Kill people? Sure, slaughter a million animals? Sure, increase the amount of oil that is produced coming from the ground? Sure. Reduce energy consumption? God forbid. Everything would crash if we were to drop energy consumption, keep moving it upwards, upwards, upwards, close your eyes everybody.

  • Tue, Feb 19, 2013 - 03:48pm

    #13
    TheWind777

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    Exponential Growth

It's funny, actually, that it seems so obvious and yet the most intelligent animal on this planet seems to be completely blind.

Lets just say that humans ARE bacteria, and that there's nothing whatsoever they can do to change the course of their bacterial growth any more than bacteria can.

From that assumption, we SHOULD be able to determine an equation which, within certain ranges of interpolation, will show us WHAT will happen and WHEN.

Just from my sorely-lacking skills, I can take the best growth curve that is not just a theoretical growth curve taken from e-coli growth, for example and with Photoshop I should be able to match the height-to-width ratio on World Population Growth.

I, of course, have DONE that. It only takes about a half-hour.

Now, you can put in a graph and see what happens.

Why don't humans do that? Because they have this stupid assumption that some external factor will somehow magically step-in (God?) and reverse the process for us because we're 'SMART'.

Well, our amount of smartness hasn't seemed to have dented the world population growth in the past 50 years (remember the 'World Population Growth' movement? It didn't dent the population growth curve one bit).

In all the assumptions people add-in other factors as if they matter such as oil production or the economy. Those are secondary factors. When people study bacteria curves they never determine just WHAT killed-off the bacteria. It doesn't MATTER. It's all a  MOOT POINT.

All you need-do when determining and interpolating what will happen with bacteria is put the growth rate in and that can be determined quite easily… by measurement.

So, hows about everybody here take what they already know about exponential growth, take the actual figures of World Population Growth and ASSUME that bacteria and us are the same. From that information, what happens… in what year does the population go into plummet, and by what amount?

I would say that, if one does such a thing, one should be able to come up with a best and worst case scenario.

I've done that, myself, using the curve for e-coli and my curves show the following:

By 2050 there are 9.1 billion people.

By 2150 the flat part of the curve is reached.

By 2200 the population starts to plummet.

By 2350 the population has reached a low of 1 million again… bacteria growth never dies-out completely-completely. Isn't that a hopeful thought?

I would suggest everybody else to do the same. Find a nice solid bacteria growth curve that is not based on theory. Use Photoshop to stretch the height-per-width ratio until the curve exactly fits the world population growth (minus the interpolation crap that supposed scientists like to tack-on to it which are so much malarky). There's the answer.

 

Now, figure that with my curve – that was worst-case. Best case is that it starts to flatten-off as short a time as 2050 and ends up at the bottom at around 2150.

Why is it that this organism has such arrogance that it thinks that it can somehow modify a curve which has not modified in the slightest bit in the past 200 years? Is there any slight dent in the curve at all, anywhere? Nope. So, we are bacteria… period. If we are bacteria, then bacterial curves should fit perfectly. If bacterial curves fit perfectly, we should be able to, quite easily, determine exactly what will happen using any old bacteria curve. Try many different bacteria curves just to make sure and that should be the answer.

Now, instead of argue about it – try it yourself. The secret it… find a bacteria curve which isn't based on theory. It has to be real measured figures of bacteria, not some curve which is based on some model equation.

 

 

 

  • Tue, Feb 19, 2013 - 03:56pm

    #16
    TheWind777

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    Argument is one of the bacterial traits

What I'm saying is so obvious; yet nobody will do it. Instead, they will perpetually argue and argue and argue until the equation I just mentioned comes up in our face in a truly obvious way.

 

So, if your first response isn't to go find an actual graph of bacteria growth… there is the problem. Argument replaces action, and that's HOW and WHY we will die exactly the same as bacteria do using their exact same curve.

We will be the first animal in known history where a handful of people showed the demise; and after-the-fact people will go, "Huh, so you were right," but weren't able to do one thing to stop the demise.

Strange how human intelligence seems to have certain limits.

It would seem that it isn't a matter of whether it will occur, it is a matter of 'just when will the knee start to flatten-out and just when will it plummet'?

And, smarter people than I am should be able to hone the concept… possibly even proving how, when taken as a group, humans act exactly like bacteria would act.

  • Tue, Feb 19, 2013 - 06:04pm

    #17

    sand_puppy

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    Bacterial Growth Curve

I hope that we develop enough perspective on this process that we can respond to it with some creativity.  It is my impression that this is exactly what "The Crash Course" and this forum is about–finding perspective on these processes, like population dynamics, that we are in the middle of.

One of the pp members, in talking about water policy, noted that "most people will not become interested in water issues until they turn the handle on the tap and nothing comes out."  Sadly, there is much truth in that.  But not for all of us.  And gathered here are some people who witness the exponential population growth curve and understand that it will be forced into an "S" shape.  We don't like this, but we have enough perspective to see the writing on the wall.  And we are owning the predicament.  ("Yep, we humans are in a pickle.")

Out of some clear seeing of what is happening, and honest owning of the predicament, some creative responses arise.

 

  • Wed, Feb 20, 2013 - 03:21pm

    #18
    TheWind777

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    The process

Well, the process I used was quite simple, actually.

I found the best bacteria curve I could which I thought was actual measurements rather than just being an ideal curve.

I brought it into Photoshop and made the background transparent, deleting the background. I then made a selection of the curve and used stroke to widen the line one pixel.

Next I took curves from the internet of World Population Growth (the problem, again, is whether you are getting real-world measured population growth curves, or whether they are just idealized curves) and used Photoshop's size gadget to distort the height/width ratio and size until the curve exactly matched the bacteria curve.

I then cloned the distance between the year markers, extending the year markers up and up and up until I had markers that went up past the year 2200.

There was certainly a range of choices… which basically had everything to do with how high the population might rise before it started flattening-out. What it showed, though, was because of the rapid plummet… you didn't have all THAT much range. You couldn't, for example, make the curve go past about 2300 without having the exponential curve not at all fit the world population curve any more.

Of course if the bacteria curve wasn't correct, then the interpolation would not be accurate. In order for it to truly be scientific… I was hoping that by spreading the idea that someone might actually take measurements from bacteria, that would give a truly accurate die-off line… or even combine the growth rates from many different kind of bacteria, creating an average die-off curve (which would probably be more like 'any population which overgrows at an uncontrolled rate'.

Finally, the world population could be better determined by taking the curves from all major continents and adding them all together into an average curve.

The secret would be… just assume that we ARE like bacteria, that our brains AREN'T any different, that the bigger controlling factors are exactly the same self-preserving factors which cause bacteria to overgrow (seeing that the World Population growth doesn't at all seem to be influenced by things such as 'Zero Population Growth' groups). and SEE where it leads.

My main problem is… am I really using curves which are true measured curves from actual bacteria colonies? And, am I truly using actual curves from true current World Population Growth numbers?

I would say, however, that even my experiments might show something important. It might give at least a range which one might go by.

The interesting thing was… not all exponential curves (World Population, Oil Production, Stock Market, GNP, U.S. Population, etc.) all end up plummeting at the same year. The worst seemed to be Capitalism. It started flattening-out in 2070, which was scary. In fact, the final flat line before the plummet was pretty short because of the exadurated rise. The faster it rose, the faster it plummeted.

Also, some countries plummetted before others did. The best was South America. The worst WASN'T the United States, strange enough.

It could be that everybody seems to be ignoring the die-off phase of the exponential curve because a pure exponential goes-off-to-infinity. American Capitalism has banked on that curve, and absolutely NEVER shows a die-off part to the exponential. When they compute the die-off exponential, they compute it as a separate curve. It has no relationship to the forward-exponential curve and therefore nobody ever integrates it.

But I figure, you already have a pure die-off curve, and that's the die-off curve of bacteria. So, if you don't have a mathematical curve, use the bacteria curve itself to do the assessments. It should give exact readings (pooh on those who have the illusion that we're 'smarter' than bacteria. The math shows that we aren't; so assume that we aren't and you should have your answer.

 

 

 

  • Wed, Feb 20, 2013 - 04:06pm

    #20
    TheWind777

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    What is there…

The first image is just a pure photo of the Bacteria graph I used from the internet.

The next five are my experiments, going best-and-worst case scenarios trying to best-fit the curve.

The next three are experments using the Stock Market curve. Sorry that StockMarket1.jpg still has the blue and red background from the World Population growth graph.

Finally are the PSD files so you could do your own experiments.

  • Wed, Feb 20, 2013 - 04:08pm

    #19
    TheWind777

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    My Experiments

So, this in no way is scientific… but it's interesting and might give people an idea.

http://thewind777.angelfire.com/exponentials.html

The last link is a zip archive containing the two PSD-formatted Photoshop layered documents.

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