Well,
A guy looses the thread for a couple days and look what happens…

Now, I don't know much about nuttin' seein' as I am just a dumb nurse…

And given that alphabet soup behind one's name don't impress me much… (other than a lot of cash has been spent)

I'd like to offer a different perspective.

Let's look at a couple quotes:

No, that's not right. The percentage can't be exponential if the percentage is constantly declining (as the percentage growth has been for approximately the last 40 years).

Here is a graph of annual percentage growth of world population from 1950 to present, and projected out to 2050:

http://www.census.gov/population/international/data/idb/worldgrgraph.php

You can see that the percentage growth has been declining steadily since 1970. Or even circa 1963. So the world population has not been increasing exponentially for approximately 40 to 50 years.

The fact that world population growth has not been exponential for a long time can perhaps be better seen by this graph, that shows the absolute number of people added worldwide every year:

http://www.census.gov/population/international/data/idb/worldpopchggraph.php

Then:

In comment #62, simonjacques points out better than I did (in comment #66) that human population is not even increasing arithmetically (what I called linearly)…let alone exponentially.

However, my comments in #66 have do have links to graphs that show how population is not even increasing arithmetically (linearly)…let alone exponentially.

Thanks, simonjacques.

Both graphs show a different story. The first one shows an overall growth* rate change* that has been already admitted here.

The next graph quoted points to an *annual population change*.

OK so far… I think. If the growth *rate* goes down, I would agree that the *annual change* in population would have to go down. But then there is this sticky graph:

Geesh, now I ain't no mathematician, but that looks linear…

Well, kind-of… The disturbing thought is that 40% of each of the graphs, well, has been interpolated. In a simple man's terms, "just ain't happened yet" or "a guess" or to appease the engineers, "a SWAG." Each of the graphs looks at a one hundred year period. (1950-2050)

To rephrase it into terms that I can understand, I have 7 billion MRSA bugs in my petri dish where I only had 3 billion 50 years earlier. OK there is still enough agar (food) to grow more bugs but I don't know how many. – *Hold onto this thought.*

So, Walla! I have made Mark's point that population growth is not exponential… although it does look linear-ish to me. (I stuck my ruler on the 'puter screen and drew a straight line… boy is my wife going to be angry that I marked up her 'puter screen.) –* Don't get out the torches and pitch forks yet for the folks over at PP yet.*

Yeah, I guess I could agree looking at 100 years of data (where 40% hasn't happened yet) and say YEAH! population growth isn't an issue. But, our country has been around for a little over 200 years. Is there any data that speaks to population growth that covers that time period?

The above graph was taken from an article by Jerry Grantham. (1938 was when he was born not me) Now dang it, what the heck is that?!? Sure looks like those *hockey stick* things that I have heard are a tell-tale sign of exponential function. And, what the heck, the real turning point appears to be around 1950 maybe 1960 – the scale is a little coarse. But that makes no sense, according to the U.S. census bureau as cited above, population growth rate has been declining since the 1960's and even the annual rate is down according to them. – *Back to this in a minute.*

Then someone said:

Using the term "exponential growth" to describe growth rates that are not even arithmetic is misleading. I suggest that this word is being used not for it's "clarifying and explanatory power" (which it lacks) but for it's emotional impact. There is a mathematical function that describes this growth pattern much more accurately: **logistic** growth. We don't live an exponential world; it's much more of a **logistic** world. Exponential functions accurately describe yeast growth in petrie dishes but very little in the outside world.

Logistic? Like logarithmic? I remember those. Here's what the brains over at Texas A&M say about that. Remember, not me, the math kids:

If you understand that **A LOG IS ANOTHER WAY TO WRITE AN EXPONENT**, it will help you tremendously when you work through the various types of log problems. One thing that I will guide you through on this page is the definition of logs. This is an important concept to have down. If you don't have it down it makes it hard to work through log related problems. I will also take you through graphing, evaluating and finding the domain of logs. I think you are ready to get started.

Here is a little YouTube video on how to graph a Log using an Excel spread sheet. Log Scales on Excel (I am not embedding the video, I have wasted too much bandwidth already)

I will go out on a limb and say this, anything that grows at an exponential (or logarithmic) rate in a confined space like a petri dish (or planet) will reach carrying capacity and then decline. The question is, (in the case of human) how much pain will be felt along the way. Oh wait, here is a link to a High School Biology book that discusses what I just wrote. Population Dynamics and Growth Patterns

The bottom line is, the world population is growing. And, it is growing at a rate that will indeed reach carrying capacity at some point sooner rather than later. What that carrying capacity point is, I do not know. I will leave that to the folks that have the alphabet soup letters behind their names to figure that out. (they have to justify all that money they spent) To quibble over whether population growth can be defined as logarithmic, exponential, linear or whatever label you want to put on it, is beside the point. Once the petri dish is full…

As for me, I see hockey sticks.

~ Peace

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